1. Past simple
The past simple is a verb tense which is used to describe finished actions or facts at a specified time in the past.
There exists both regular and irregular verbs.
Regular verbs: The past simple is formed by adding - ED to the verbal basis. Consequently "**to walk"will become"**walked".
Irregular verbs: For irregular verbs, the form changes. For example, "to go" will become "went".
- Example: Yesterday I went to the post office to buy a stamp.
The auxiliary didn’t is used to make a negative.
- Example: Helen didn’t miss her train.
The auxiliary did is used to make a question.
- Example: Did you eat at a restaurant last night?
The past simple of the verb to be is: was/wereandwasn't/weren'tfor the negative.
- Example: Sandrine and Virginia weren’t very honest with their team.
We use the past simple with specific expressions such as: yesterday/ago/last night/dates/years/last year/when..
2. Present Perfect
The present perfect is a verb tense which is used to show that an action has taken place once or many times before now and usually at an unspecified time.
The present perfect is formed using have/has + past participle.
- Example: I have been to London many times.
Questions are made by inverting the subject and have/has.
- Example: Have you ever eaten sushi?
Negatives are made with haven’t/hasn’t.
Present perfect uses:
1- Unspecified Time in the past
We use the present perfect to say that an action happened at an unspecified time in the past. The exact time is not important. You cannot use the present perfect with specific time expressions such as: yesterday, one year ago, last week, when I was a child, when I lived in Japan, etc.
We can use the present perfect with unspecific time expressions such as: ever/ never / many times / so far / already / yet / just / this week...
You can use the present perfect to describe duration with non-continuous verbs, often using for/since.
Here is a list of non-continuous verbs: to be, to want, to cost, to seem, to need, to care, to contain, to exist, to believe, to own, to belong, to have, to like, to love, to hate, to dislike, to fear
- Example: This company has existed since 1997.