Since for yet and already in present perfect tense

Irregular verbs have irregular past participles . Sometimes the past participle of an irregular verb is the same as the past simple form and sometimes it is different.

have, had → had lose, lost → lost
do, did → done eat, ate → eaten

We use the present perfect to talk about present activities that started in the past. We use for to talk about the period of time up to the present, e.g. for four years , for two days .

The company has been in business for four years .

We use since to talk about the time when an activity started. This can be a date, a day, a month, a time or an event, e.g. since 1903 , since yesterday , since May , since 8 a.m. , since my birthday , since I was ten years old .

I 've been here since 8 a.m.
I haven't seen you since the wedding .

We often use the past simple after since .

She 's had that car since she started learning to drive.

We use the question form How long …? to ask about the period of time an activity has continued for. We can reply with for + the period of time …

‘ How long have you known Maya? ’ ‘ For six years . ’

… or we can reply with since + the time when the activity started.

‘ How long have you known Maya? ’ ‘ Since I was twelve . ’