The future perfectThe aspect expressing completion. E.g.: He’s finished university. continuousThe aspect expressing duration, formed with be + verb-ing. E.g.: What are you doing? tenseA grammatical category that is marked by verb inflection. To express when an event or action happens in time or when a state exists, we use tenses. is used for eventA general term expressing that somebody or something does something or that something happens. E.g.: An apple fell on Isaac’s head.s which will have been in progressAn action is in progress when it is happening. E.g.: When I arrived he was surfing. ("he was surfing") at a definiteRelating to a specific or determined person, thing, idea or time. E.g.: I know the guy you are talking about. ("the guy you are talking about") point of timeA particular moment in time. E.g.: She came home at six. ("six") I was born in 1980. ("1980") in the future. It relates to the future perfect tense in the same way as the present perfect continuous relates to the present perfect, or the past perfect continuous to the past perfect (durationA concept, related to the continuous aspect, expressing that an action is in progress. E.g.: What are you doing? and result/completionA concept, related to the perfect aspect, expressing that an action has finished. E.g.: He’s finished university.).

The future continuousThe aspect expressing duration, formed with be + verb-ing. E.g.: What are you doing? tenseA grammatical category that is marked by verb inflection. To express when an event or action happens in time or when a state exists, we use tenses. can express that an eventA general term expressing that somebody or something does something or that something happens. E.g.: An apple fell on Isaac’s head. will be in progressAn action is in progress when it is happening. E.g.: When I arrived he was surfing. ("he was surfing") at a certain moment in the future. This moment needs to be mentioned or implied. If it is mentioned, a time expressionA word or group of words used in a particular situation. E.g.: Good morning, at six, on the sofa or a time clauseA group of related words containing a subject and a verb. can be used.

In time clauseA group of related words containing a subject and a verb.s that refer to future time (for example clauses with after, as soon as, until, when, while etc.) we use present tenseA grammatical category that is marked by verb inflection. To express when an event or action happens in time or when a state exists, we use tenses.s.

The prepositions for and since are often used with the present perfectThe aspect expressing completion. E.g.: He’s finished university. tenseA grammatical category that is marked by verb inflection. To express when an event or action happens in time or when a state exists, we use tenses.. For is used with an incomplete period of timeA period of time that includes the time of speaking. E.g.: I have known him for two years. ("for two years"), while since with a point of timeA particular moment in time. E.g.: She came home at six. ("six") I was born in 1980. ("1980") .

The present continuous tenseA grammatical category that is marked by verb inflection. To express when an event or action happens in time or when a state exists, we use tenses. expresses that an actionA general term expressing that somebody or something does something is in progressAn action is in progress when it is happening. E.g.: When I arrived he was surfing. ("he was surfing") at the time of speakingA point of time at which an utterance is made..

"What are you doing?"
"I am reading a book."

The past perfect continuous is used to express that an actionA general term expressing that somebody or something does something started before a point of timeA particular moment in time. E.g.: She came home at six. ("six") I was born in 1980. ("1980") in the past and that (a) it was still in progressAn action is in progress when it is happening. E.g.: When I arrived he was surfing. ("he was surfing") or (b) it had just stopped. This point can be defined with a time expressionA word or group of words used in a particular situation. E.g.: Good morning, at six, on the sofa or a clauseA group of related words containing a subject and a verb.. This clause is in the past simple. 

The past simple is used to refer to a point in the past at which another eventA general term expressing that somebody or something does something or that something happens. E.g.: An apple fell on Isaac’s head. was in progressAn action is in progress when it is happening. E.g.: When I arrived he was surfing. ("he was surfing"), had been completeA concept, related to the perfect aspect, expressing that an action has finished. E.g.: He’s finished university.d or had been going on for some timeA concept which is related to our perception of reality; that part of existence which is measured in seconds, minutes, hours, days, weeks, etc.. In this way, the past simple serves as a time markerA verb or auxiliary that marks the reference point of a non-finite form. E.g.: The telephone is known to have been invented by Bell. ("is") He denied being in love with the suspect. ("denied") He must have arrived late. ("must") in subordinate time clauseA group of related words containing a subject and a verb.s of complex sentences, where the main clauseA clause that could be a sentence in itself. E.g.: I wouldn’t go there if I were you. ("I wouldn't go there") When I arrived he was surfing. ("he was surfing") is in the past continuousThe aspect expressing duration, formed with be + verb-ing. E.g.: What are you doing?, past perfectThe aspect expressing completion. E.g.: He’s finished university., or past perfect continuous tenseA grammatical category that is marked by verb inflection. To express when an event or action happens in time or when a state exists, we use tenses.s.

The past continuous is used to refer to actionA general term expressing that somebody or something does somethings in progressAn action is in progress when it is happening. E.g.: When I arrived he was surfing. ("he was surfing") at or around a particular point of timeA particular moment in time. E.g.: She came home at six. ("six") I was born in 1980. ("1980") in the past. This point can be implied, or expressed with a time expressionA word or group of words used in a particular situation. E.g.: Good morning, at six, on the sofa, or a clauseA group of related words containing a subject and a verb. with a verbA part of speech that expresses an action or a state. E.g.: John seldom plays tennis. in the past simple tenseA grammatical category that is marked by verb inflection. To express when an event or action happens in time or when a state exists, we use tenses.:

The past simple is used for actionA general term expressing that somebody or something does somethings which are completed at a definiteRelating to a specific or determined person, thing, idea or time. E.g.: I know the guy you are talking about. ("the guy you are talking about") point of timeA particular moment in time. E.g.: She came home at six. ("six") I was born in 1980. ("1980") in the past. This point can be implied, or expressed with a time expressionA word or group of words used in a particular situation. E.g.: Good morning, at six, on the sofa or a clauseA group of related words containing a subject and a verb.:

have + been + verb-ing

The perfectThe aspect expressing completion. E.g.: He’s finished university. continuousThe aspect expressing duration, formed with be + verb-ing. E.g.: What are you doing? is not considered as an aspectA verbal category relating an action to the passage of time. It can express duration or completion. in itself; rather it is the combination of the perfect and continuous aspects.