TENSE

Present Simple Tense

The present simple is used for established facts and things in general.	"A banana is never quite straight." "Malaysia exports rubber."
It is also used for habitual activities or routines.	"The President gets up at five and starts work at seven."
The simple tenses are generally used with verbs of perception: sound, seem, appear, smell, taste, look and feel (note, however, that look and feel can also be used with the continuous tenses). Base verb (+ es/es for third person)	"Going to Fiji sounds just great because the beaches appear less crowded and the prices seem quite reasonable." "This French bread smells quite fresh, tastes delicious, feels very soft, and looks just great." COMPARE: "I am not feeling very well today" and "You are looking wonderful in that new dress, my dear, but what happened to the curtains?"
The present simple is used with hear, and with see (except when it means "to meet").	"I hear footsteps. Quick, someone's coming!" "I see you don't understand what I mean." COMPARE: "She is seeing the dentist tomorrow."
The simple tenses are always used with so called state (or stative) verbs, such as: agree, approve of, believe, belong to, consider (hold an opinion), consist of, contain, cost, depend, disagree, gather (understand), hate, have (own), know, like, loathe, love, mean, own, need, possess, prefer, realize, regret, remember, resemble, suppose, think (hold an opinion), understand, want, wish, etc.	"Some people believe in UFOs, but I think they're misguided." "Henry regrets what he did and wishes to make amends.'' "Although, of course, I don't normally approve of gossip, I do like her new autobiography. It contains a number of shocking revelations about the world of showbiz."
The present simple is usually used with so called performative verbs (i.e. utterances that actually constitute an action), such as: accept, acknowledge, admit, advise, apologize, assume, deny, guarantee, hope, inform, predict, promise, recommend, suggest, warn, etc.	"He admits he made a big mistake, acknowledges full responsibility, accepts the consequences, apologizes from the bottom of his heart, and promises not to do it again."
It is used for schedules drawn up by others.	"His ship sails at dawn." "The next train leaves at half-past six."
It is often employed when telling jokes or funny stories.	"A man wanders into a restaurant and says he can eat a horse. The waiter tells him he's come to the wrong place."
The present simple is favored by live sports commentators for word economy, and to convey a sense of excitement and directness.	"Federer leads four games to one in the first set." "The crowd roars as Tyson takes a huge bite out of Holyfield's ear."
The present simple is also preferred in newspaper headlines for succinctness where space is at a premium.	"Iraq Invades Kuwait" "Man Steals Clock, Faces Time" "Fake Cardiologist Breaks Woman's Heart"

Present Continuous Tense

The present continuous is used for temporary actions or events going on at or around the time of speaking.	"The electrician is mending a fuse." "It's snowing." "In London, John is staying at the Savoy."
It is used for self-made schedules, generally for the not too distant future.	"Lucia's leaving for Milan after lunch." "Dan and Crystal are getting married in June."
It is also used for longer-term enterprises.	"He's studying hard to become a doctor." "Mitt Romney's running for President."
Used with adverbs of (high) frequency to express disproval of annoying habits.	"He is always complaining." "She's forever losing her keys."
The present continuous also used to set the scene for jokes or funny stories told in the present simple.	"This guy is sitting all by himself in a bar looking pretty inebriated, so the barman refuses to serve him another drink."
The present continuous of to be is used to react to behavior perceived as uncharacteristic for someone.	"He really is being stupid" (meaning this person is normally more sensible). COMPARE: "He really is stupid" (meaning he is stupid all the time).
The present continuous must be used with have when it is an action verb.	"She is having another baby / filet steak for dinner / a shower / a heart attack / etc."
Remember that so called state verbs cannot be used in continuous tense forms. am/is/are + present participle:	"She is having has a lot of money." "She is knowing knows how to fly a plane" "He is preferring prefers coffee to tea."

Present Perfect Tense

The present perfect connects the recent past with the present. It explains the impact of a recent activity or occurrence on present circumstances.	"Someone has eaten my sandwiches (which explains why now the plate is empty and I'll have to go hungry)." "I've lost my passport (hence I can't leave the country)."
American English prefers the simple past tense to convey personal news. It thereby loses the subtlety of British English to clearly distinguish between recent and not so recent events.	"I lost my passport." (Today? Last week? Last year?)
It is used for breaking news headlines or when wishing to emphasize that something has occurred rather than exactly when it occurred.	"Two lions have escaped from Chessington Zoo." "Powerful tornadoes have hit Mississippi, Louisiana and Arkansas"
The present perfect is used with already, just and yet.	"Samantha has already left, but Cindy has just arrived, so I guess the party hasn't finished yet."
Note that American English often uses the simple past tense with already, just and yet.	"Samantha already left, but Cindy just arrived, so I guess the party didn't finish yet."
It is used to refer to a person's entire life experience since they were born.	"Dan has traveled a great deal, but he has never been to Greenland."
It is used with ever to question a person's entire life experience of something in particular.	"Have you ever seen a straight banana?" "Has Chuck ever done an honest day's work in his life?"
American English, on the other hand, prefers the simple past tense with ever.	"Did you ever see a straight banana?" "Did Chuck ever do an honest day's work in his life?"
The present perfect is also used to quantify something done, or progress made so far. Has/have + past participle:	"Harry has driven 200 miles since breakfast." "Meg has saved $8,000 toward her new BMW."

Present Perfect Continuous Tense

Used to emphasize activities that were in progress right up to or shortly before the time of speaking and so have a direct influence on the current situation.	"She has been using a computer all day (so her eyes are now bloodshot)." "Someone has been eating my sandwiches (so half of them are missing)."
Used with for or since to say how long an ongoing or continuing activity has been in progress.	"Harry has been driving for three hours." "Meg has been saving for her BMW since last summer."
In many other cases the present perfect continuous can be exchanged for the present perfect simple, although when the latter is chosen one tends to feel that change might be in the offing.	"I've been living here for ten years (in other words, I feel almost like a native)." "I have lived here for ten years (so perhaps it's about time I moved on to pastures greener)."
Remember that so called state verbs cannot be used in continuous tense forms. Has/have + been + present participle:	"I have been knowing known Samantha for 19 years."

Past Simple Tense

The past simple is used for activities or events completed at a specific time in the past (which is either understood or indicated by a time expression).	"Manchester United thrashed Chelsea 4:1." "The ice sculptures attracted many visitors." "Most of the bars closed at midnight."
It is used for two or more completed past activities or events that occurred in sequence rather than in parallel.	"I went into town at ten, booked my summer holiday at the travel agent's, ate lunch at Pizza Hut, saw the new Bond film at the Odeon cinema, did my shopping for the weekend, and arrived home in time for tea at four."
The past simple corresponds to the foreground in a painting. It is used for the action in a story for which the past continuous sets the scene.	"The rock group were performing when the earthquake struck. Nobody noticed."
It is used with adverbs of frequency to talk about repeated actions or events in the past; would and used to are also used to talk about past habits and routines.	"Former British Prime Minister Margaret Thatcher often slept only four hours a night. She would go to bed at one in the morning and get up at five to read the morning papers. The first thing she used to check was what they were saying about her."
It is used with verbs of perception: sound, seem, appear, smell, taste, look and feel (note that look and feel can also be used with the continuous tenses).	"The bread smelt fresh, tasted delicious, felt very soft and looked just great." COMPARE: "Max wasn't feeling at all well today. He really was looking under the weather."
The simple tenses are always used for so called state verbs such as agree, approve of, believe, belong to, consider (hold an opinion), consist, contain, cost, depend, disagree, gather (understand), hate, have (own), know, like, loathe, love, mean, own, need, possess, prefer, realize, regret, remember, resemble, suppose, think (hold an opinion), understand, want, wish, etc.	"The minister was agreeing agreed to resign, even though he wasn't thinking didn't think he was needing needed to."
The past simple is usually preferred with so called performative verbs (i.e. utterances which actually constitute an action) such as: accept, acknowledge, admit, advise, apologize, assume, bet, deny, guarantee, hope, inform, predict, promise, recommend, suggest, warn, etc.	"Although the rich oil sheik promised (was promising) the Hollywood actress ten million dollars in cash, a brand new Mercedes, and a house in Palm Beach, her lawyer advised her not to marry him."

Past Continuous Tense

The past continuous corresponds to the background in a painting. It sets the scene for all the action reported in the past simple.	"I was leaning back in my armchair staring up at the night sky. The moon was beaming brightly. All the stars were twinkling. Then it came to me: I would have to get the roof fixed."
It is used for temporary actions or events that were going on at or around a particular time in the past when something of shorter duration occurred.	"While I was waiting for the ferry, I ate lunch in a sushi bar. And while I was wolfing down my sushi, one piece of fish started moving."
It is also used for two activities of similar duration that were going on in parallel.	"I was washing the car while my wife was cleaning the house."
Remember that so called state verbs cannot be used in continuous tense forms.	"I was knowing knew Samantha very well."

Past Perfect Tense

This tense is used to talk about the pre-past, i.e. activities or events completed before (but relevant to) subsequent activities or events referred to in the past simple.	"I had just prepared a candlelight dinner for two when the Jehovah's Witnesses called." "Rosalind, who had climbed ten flights of stairs, was now quite breathless." "Mandy had studied Finnish for 3 years before she emigrated to Finland."
If, however, the second action is a direct result of the first, then the past simple is used for both.	"When the artist had finally appeared on stage, everyone applauded."
The past perfect tense is used to report on past intentions that were sadly never realized. Had + past participle:	"The boss had hoped to slip off to the golf course for the rest of the afternoon, but head office wanted to speak to him about disappointing sales figures."

 Past Perfect Continuous Tense

The past perfect continuous is used to report on an activity of interest or direct relevance that was still in progress up until or immediately prior to a subsequent event in the past.	"When the chemistry teacher returned to the lab, he sniffed and stopped smiling. Someone had been making a stink bomb." "Police arrested the chief executive whose chain of restaurants had been cooking the books."
Remember that so called state verbs cannot be used in continuous tense forms.	"In 1994, I had already been knowing known Samantha for 10 years."

Future Simple Tense

WILL: used to express pure futurity (i.e. without any element of willpower).
WILL: used when making predictions based upon one's knowledge of a person's character.
WILL: used for plain, informal requests, as well as orders given to subordinates.
WILL: used with emphasis to express irritation over the bad habits of others.
WILL/SHALL: used for spontaneous offers or plans made at the time of speaking, or to agree to something.
WILL/SHALL: used for promises.
SHALL: sometimes used instead of WILL in the first person singular and plural in more formal style to express futurity, especially in cases where the element of willpower is involved.
SHALL: used when seeking others' approval of offers or suggestions.
SHALL: used to elicit more information.
GOING TO: used to talk about plans already made before the time of speaking.
GOING TO: used when forecasting what is likely or inevitable because all the signs are there.
PRESENT CONTINUOUS: often used instead of GOING TO for self-made plans and voluntary schedules, especially for the not too distant future.
PRESENT CONTINUOUS: usually preferred to the GOING TO future with GO and COME.
PRESENT SIMPLE: used for schedules decided by others.

 Will+verb
Am/is/are + going to + verb
I will watch the news / I am going to watch the news.

Future Continuous Tense

Used for actions or events forecast to be in progress at or around a particular time in the future.
Used for future events that are the result of previous arrangements or decisions.
The future continuous tense can be used instead of the present continuous with future meaning.
It is also used to make extra polite enquiries about someone's future plans.
Remember that so called state verbs cannot be used in the continuous tense forms. Will be + present participle Am/is/are + going to be + present participle: I will be watching the news at 9pm. / I am going to be watching the news at 9pm.

Future Perfect Tense

Used for activities or events forecast to be completed by a particular time in the future.
Used to quantify progress forecast to have been made at a given time in the future.   Will have + past participle Am/is/are + going to have + past participle I will have watched the news before 10pm. / I am going to have watched the news.

Future Perfect Continuous Tense

Used for activities forecast still to be in progress at some time in the future.
Remember that so called state verbs cannot be used in continuous tense forms.   Will have been + present participle Am/is/are + going to have been + present participle: I will have been watching the news for over ten minutes before you join me. / I am going to have been watching the news for over ten minutes before you join me.

https://www.ecenglish.com/learnenglish/lessons/english-grammar-tenses

http://www.davidappleyard.com/english/tenses.htm

https://www.grammarly.com/blog/verb-tenses/