How to say ‘for’ with time and duration

To say things like for a week and for two months in Irish, you need to know whether the duration occurs in the past or in the future.

How to say I have been here for a week

If you are describing something that started in the past and is still in progress at present, you must use a verb in the present tense in combination with the preposition le and, optionally, the adverb anuas.

Tá mé anseo le seachtain.  I have been here for a week.

Tá mé i mo chónaí in Éirinn le dhá bhliain.  I have been living in Ireland for two years.

Tá mé anseo le seachtain anuas.  I have been here for a week.

Tá mé i mo chónaí in Éirinn le dhá bhliain anuas.  I have been living in Ireland for two years.

The preposition le normally means with but here it has the same function as for in English. Note that the verb must be in the present tense (tá mé etc.), never in the past tense (bhí mé etc.).

How to say I will be here for a week

If you are describing something that is going to happen in the future (regardless of whether it has already started or is yet to start), you use the compound preposition go ceann followed by the duration. The noun phrase that expresses the duration must be in the genitive case:

Beidh mé anseo go ceann seachtaine.  I will be here for a week.

Beidh mé i mo chónaí in Éirinn go ceann dhá bhliain.  I will be living in Ireland for two years.

Other combinations that often come up include:

go ceann lae  for a day

go ceann dhá lá  for two days

go ceann coicíse  for a fortnight, for two weeks

go ceann míosa  for a month

go ceann sé mhí  for six months

go ceann bliana  for a year

You can of course employ other verbs besides bí be. For example, you can use this construction to talk about your travel plans.

Rachaidh mé go Londain go ceann cúpla lá.  I will go to London for a couple of days.

If you wanted to get very literal, you could rephrase go ceann as until the end of. The noun ceann, which you may know as the word for head, appears here in its less common meaning of end, endpoint.

A third option

If what you want to say does not fit any of the two descriptions above, then there is a third option you can use. This involves the compound preposition ar feadh followed by the duration. Again, the noun phrase that expresses the duration must be in the genitive case.

For example, you can use this to talk about things that both started and ended in the past.

Bhí mé in Éirinn ar feadh seachtaine.  I was in Ireland for a week.

You can also use it to talk about things that happen repeatedly or habitually.

Bím in Éirinn ar feadh tréimhsí.  I am often in Ireland for periods of time.

The compound preposition ar feadh can be rephrased as for the duration of or along the length of. It can be combined with durations that occur anytime: past, present or future. You can even use it instead of the two constructions described above, but that is uncommon.

Bonus: how to say for long

With the preposition le, the expression is le fada.

An bhfuil tú ag fanacht le fada?  Have you been waiting (for) long?

With the compound preposition go ceann, the expression is go ceann i bhfad.

An mbeidh tú ag fanacht go ceann i bhfad?  Will you be waiting (for) long?

With the compound preposition ar feadh, the expression is ar feadh i bhfad.

An raibh tú ag fanacht ar feadh i bhfad?  Were you waiting (for) long?

An mbíonn tú ag fanacht ar feadh i bhfad?  Do you usually wait (for) long?