The future 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. expresses 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 completeA concept, related to the perfect aspect, expressing that an action has finished. E.g.: He’s finished university.d before a point in the future. This event may happen at any time up to that point. It is normally used with time expressionA word or group of words used in a particular situation. E.g.: Good morning, at six, on the sofas and clauseA group of related words containing a subject and a verb.s beginning with by.

In contrast with the present perfectThe aspect expressing completion. E.g.: He’s finished university. 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., which emphasisSpecial importance or attention given to something. E.g.: All I wanna do is have some fun.es the result of a completeA concept, related to the perfect aspect, expressing that an action has finished. E.g.: He’s finished university.d actionA general term expressing that somebody or something does something, the present perfect continuousThe aspect expressing duration, formed with be + verb-ing. E.g.: What are you doing? tense focusThe main or central point of attention or interest; what is emphasized. E.g.: All I wanna do is have some fun. ("all")es on the durationA concept, related to the continuous aspect, expressing that an action is in progress. E.g.: What are you doing? or the activity itself.

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. is used to express actionA general term expressing that somebody or something does somethings happening in an incomplete period of time. An incomplete period is one which includes the present moment, that is, the time of speakingA point of time at which an utterance is made.. For example, the time expressionA word or group of words used in a particular situation. E.g.: Good morning, at six, on the sofas today, this week, this year, in my life etc. all refer to such a period.

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. is used for recent actionA general term expressing that somebody or something does somethings that have a result in or an effect on the present.

Someone has opened the window.

Here we want to emphasisSpecial importance or attention given to something. E.g.: All I wanna do is have some fun.e that the window is open. The sentence suggests that it is probably cold inside. Compare with this one:

Check the following contrast between the past perfectThe aspect expressing completion. E.g.: He’s finished university. and the past perfect continuousThe aspect expressing duration, formed with be + verb-ing. E.g.: What are you doing?. The former emphasisSpecial importance or attention given to something. E.g.: All I wanna do is have some fun.es completionA concept, related to the perfect aspect, expressing that an action has finished. E.g.: He’s finished university. while the latter emphasises the activity or its durationA concept, related to the continuous aspect, expressing that an action is in progress. E.g.: What are you doing? .

By 6 he had eaten all the food. (there was nothing left)
He put down the fork he had been eating with and left the table.

We use the past perfect 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. to 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. took place before another event in the past, that is, it had been completeA concept, related to the perfect aspect, expressing that an action has finished. E.g.: He’s finished university.d. This tense allows us to keep track of the order of the events if this is not clear otherwise.

have + past participle 

The actionA general term expressing that somebody or something does something expressed with the perfectThe aspect expressing completion. E.g.: He’s finished university. participle happens before another one.

Having seen the film before, I didn’t feel like going to the cinema. (= As I had seen the film before, I didn’t feel like going to the cinema.)

The aspect of a verbA part of speech that expresses an action or a state. E.g.: John seldom plays tennis. does not mark when an actionA general term expressing that somebody or something does something takes place in timeA concept which is related to our perception of reality; that part of existence which is measured in seconds, minutes, hours, days, weeks, etc., but shows the relationship between the action and the passage of time, seen from the speaker's point of view.

There are two aspects in English: the continuousThe aspect expressing duration, formed with be + verb-ing. E.g.: What are you doing? (also called progressAn action is in progress when it is happening. E.g.: When I arrived he was surfing. ("he was surfing")ive) aspect expresses durationA concept, related to the continuous aspect, expressing that an action is in progress. E.g.: What are you doing? ; the perfectThe aspect expressing completion. E.g.: He’s finished university. aspect expresses completionA concept, related to the perfect aspect, expressing that an action has finished. E.g.: He’s finished university..