TEMPORAL CLAUSES and adverbial time clauses, condiitonal and time clauses, present perfect use links

Temporal Clauses

The time clauses in the English language are introduced by conjunctions such as after, as soon as, before, till, until, when, whenever, while or time expressions such as the minute, the moment etc.
We do not use the Future tense (will) in a time clause to describe future activities (in this respect, it is similar to IF clauses).

Temporals are time expressions after which you use a verb in the Present Simple tense.

when	since	while	until/till
whilst (formal)	as	whenever /when	as soon as
after	by the time	before	once

1. When the time clause refers to the present or the past, the verb has the same tense that would be used in a single clause.

Example:

1. When he left school, he was fifteen. (He left school. He was fifteen.)
2. Whenever I am in England, I visit our partner university.
3. He waited until everybody had gone.

2. When the time clause refers to the future, the Present Simple/Present Perfect tense is used.

Dependent clause	Independent clause
Present/Present perfect tense	Future tense/Imperative

Examples:

1.     Don´t start the experiment until everybody is here.

2.     Switch off the lights before you leave the lab.

3.     When I finish/After I have finished my PhD studies, I will work in a research institute.

4.     As soon as I receive/have received my degree, I´ll go abroad.

5.      I will not stop trying until I obtain/have obtained the expected result.

Note: The present perfect tense is used to stress completion of an activity.

SINCE

Independent clause	Dependent clause
Present perfect tense	Past tense

I haven´t seen him since we graduated (in 2010).

Notes:

- When “when” relates to the time we want to know , it can be followed by “will” + infinitive. Present continuous is also often used here.

He wants to know when they will come/they are coming.

- “Since” and “as” are also used in reason clauses as formal alternatives to because.

The solution is promising since/as it can work during transients.

The meaning of the following sentence can be interpreted in two ways:

 As prices rise, the demand for higher wages increases. (= the demand increases because prices rise or: the demand increases at the same time as prices do)

- “while” also expresses contrast

George was interested in research while his brother was more practically orientated.

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Adverbial Time Clauses Slides

Conditional and Time Clauses

Slideshow