The Immediate Present Tense
As stated above, bí has two present tenses -- immediate (something which is right now) and habitual (something which usually is). The immediate present tense of bí is used to describe the subject (appearance, manner, etc), where the subject is, what the subject is doing, or what state the subject is in. As stated above, it does NOT tell WHAT something is. Note that except for the alternate 1st person forms, the same word is used for ALL persons -- unlike English, which uses am, is and are.

tá mé -- I am ... or ... táim
tá tú -- you are
tá sé -- he is
tá sí -- she is
tá muid -- we are ... or ... táimid
tá sibh -- y'all are
tá siad -- they are

Examples:
Tá mé anseo anois -- I am here now
Tá Seán ag rith -- Seán is running
Tá sí ina seasamh -- She is standing (literally, in her standing)

Bí is irregular in the immediate present tense, meaning that when a helper word is used (ní, an, nach, go, etc) the root changes -- in this case from tá to fuil. Remember that ní lenites the following verb -- ní + fuil >> ní fhuil. Also remember that fh is silent and so 'ní fhuil' sounds like 'níl', which is how this is written now, and has been written for several hundred years. A dialectical variant to ní is chan, which would be written chan fhuil.

níl mé -- I am not ... or ... nílim
níl tú -- you are not
níl sé -- he is not
níl muid -- we are not ... or ... nílimid
níl sibh -- y'all are not
níl siad -- they are not

Examples:
Níl mé thuas an staighre -- I am not upstairs
Níl Seán ag siúl -- Seán is not walking
Níl sí go deas -- She is not nice

The helper word an creates the question and eclipses the following verb -- in this case fuil -- an + fuil >> an bhfuil.

an bhfuil mé? -- am I? ... or ... an bhfuilim?
an bhfuil tú? -- are you?
an bhfuil sé? -- is he?
an bhfuil sí? -- is she?
an bhfuil muid? -- are we? ... or ... an bhfuilimid?
an bhfuil sibh? -- are y'all?
an bhfuil siad? -- are they?

Examples:
An bhfuil mé sa rang ceart? -- Am I in the correct class?
An bhfuil Seán ag leamh? -- Is Seán reading?
An bhfuil sí ard? -- Is she tall?

The helper word nach creates the negative question and eclipses the following verb -- in this case fuil -- so nach + fuil >> nach bhfuil.

nach bhfuil mé? -- am I not? ... or ... nach bhfuilim?
nach bhfuil tú? -- aren't you?
nach bhfuil sé? -- isn't he?
nach bhfuil sí? -- isn't she?
nach bhfuil muid? -- aren't we? ... or ... nach bhfuilimid?
nach bhfuil sibh? -- aren't y'all?
nach bhfuil siad? -- aren't they?

Notice that except for the first-person forms, all other persons use the exact same form as the third person. From now on, in order to save space, I will only show a form if it is different from the third-person form.

The Habitual Present Tense
The other form of the present tense denotes a habitual or repetitive action, one that occurs on a regular basis. English doesn't have anything like this and must rely on other means to denote a habitual action -- He is in school every day; Mary dances on Saturdays. The use of the habitual present tense is sufficient to indicate a repetitive action, although additional information is often added for clarification. The habitual present of bí is fully regular.

bím -- I am ... (not bíonn mé)
bíonn sé -- he is
bímid -- we are ... or ... bíonn muid

Remember that the third-person form (bíonn) is used for ALL other persons -- bíonn tú {you are}, bíonn siad {they are}, etc.
Examples:
Bíonn tú ar scoil Dé Máirt -- You are at school on Tuesdays
Bíonn Seán anseo -- Seán is (usually) here

The helper word ní forms the negative with lenition of the verb. Because the habitual present tense is regular, the verb root doesn't change.

ni bhím -- I am not
ní bhíonn sé -- he is not
ní bhímid -- we are not

Examples:
Ní bhím ansin ar maidin -- I'm not there in the morning
Ní bhíonn na laethanta grianmhar -- The days are not (usually) sunny

The helper word an forms the question with eclipsis of the verb.
The helper word nach forms the negative question with eclipsis of the verb.

An mbím? -- Am I?
An mbíonn sé? -- Is he?
An mbímid? -- Are we?
Nach mbím? -- Am I not?
Nach mbíonn sé? -- Isn't he?
Nach mbímid? -- Are we?

Examples:
An mbíonn siad tuirseach go minic? -- Are they often tired?
Nach mbíonn tú tuirseach tar éis obair? -- Aren't you tired after work?

The Past Tense - An Aimsir Chaite
There a few things to notice about the past tense of bí.

1 the past tense is simply the command form (bí) lenited -- this is the general rule for all verbs
2 there is an alternate form for the 3rd person plural, otherwise the same form is used for all persons
3 when a helper word is used, the root changes from bhí to raibh -- as with the present change from tá to fuil
4 helper words ní, an & nach are used, instead of the normal past tense helpers níor, ar & nár

bhí mé -- I was
bhí sé -- he was
bhí muid -- we were ... or ... bhíomar
ni raibh mé -- I wasn't
ní raibh sé -- he wasn't
ní raibh muid -- we weren't ... or ... ní rabhamar
an raibh mé? -- was I
an raibh sé? -- was he?
an raibh muid? -- were we? ... or ... an rabhamar?
nach raibh mé? -- wasn't I?
nach raibh sé? -- wasn't he?
nach raibh muid? -- weren't we? ... or ... nach rabhamar?

The Future Tense - An Aimsir Fháistineach
The future tense is completely regular.

beidh mé -- I will be
beidh sé -- he will be
beidh muid -- we will be
ni bheidh mé -- I won't be
ní bheidh sé -- he won't be
ni bheidh muid -- we won't be

an mbeidh mé? -- will I be?
an mbeidh sé? -- will he be?
an mbeidh muid? -- will we be?
nach mbeidh mé? -- won't I be?
nach mbeidh sé? -- won't he be?
nach mbeidh muid? -- won't we be?

The Habitual Past Tense - An Aimsir Ghnáthchaite
This tense indicates a habitual, recurring state in the past. Note that there are many unique forms for this tense -- only the third-person singular and first- and second-person plural share the bhíodh form.

bhínn -- I used to be ... (not bhíodh mé)
bhíteá -- you used to be ... (not bhíodh tú)
bhíodh sé -- he used to be
bhíodh sí -- she used to be
bhíodh muid -- we used to be ... or ... bhímis
bhíodh sibh -- y'all used to be
bhídís -- they used to be ... (not bhíodh siad)

I will only show the third-person form (bhíodh) with the helper words. Realize that the pattern applies to ALL persons.

ní bhíodh sé -- he didn't used to be
an mbíodh sé? -- did he used to be?
nach mbíodh sé? -- didn't he used to be?

The Conditional Mode - An Modh Coinníollach
This tense is correctly called a "mode", because there is no certainty that the action ever happened or will ever happen, unlike the tenses which describe actions which have happened, will happen, or are happening now. Note that, like the habitual past tense, only the third-person singular and first- and second-person plural share the bheadh form.

bheinn -- I would be ... (not bheadh mé)
bheifeá -- you would be ... (not bheadh tú)
bheadh sé -- he would be
bheadh sí -- she would be
bheadh muid -- we would be ... or ... bheimis
bheadh sibh -- y all would be
bheidís -- they would be ... (not bheadh siad)

I will only show the third-person form (bheadh) with the helper words. Realize that the pattern applies to ALL persons.
ní bheadh sé -- he wouldn't be
an mbeadh sé? -- would he be?
nach mbeadh sé? -- wouldn't he be?

The Command Form - An Modh Ordaitheach
The command form is bí
Bí ciúin = Be quiet; Bí cúramach = Be careful.

The plural command form is bígí
Bígí ciúin, a pháistí = Be quiet, children.

The third-person command form is bíodh
Bíodh imní ort = Be worried -- literally (Let) Worry be on you.

The other command forms needn't trouble you at this point.
Remember, ná makes the negative command
Ná bí anseo amárach = Don't be here tomorrow.

Before you go on to further verbs, you must learn the verb "be". This is probably the most widely used verb in Irish (or any language, for that matter). In Irish, it has two different present tenses, depending on whether the action is immediate or habitual. It is irregular in the immediate present tense and the past tense. In all other tenses it is fully regular. No matter which tense or form the verb bí is in, it can only be used to describe the subject or tell what state the subject is in, NOT define what the subject is. There is a different, unrelated verb, the copula, which is used for identification and various grammatical functions. It will explained in another lesson.

The Present Tense - An Aimsir Láithreach

The Immediate Present Tense
As stated above, bí has two present tenses -- immediate (something which is right now) and habitual (something which usually is). The immediate present tense of bí is used to describe the subject (appearance, manner, etc), where the subject is, what the subject is doing, or what state the subject is in. As stated above, it does NOT tell WHAT something is. Note that except for the alternate first-person forms, the same word is used for ALL persons -- unlike English, which uses am, is and are.

tá mé -- I am ... or ... táim
tá tú -- you are
tá sé -- he is
tá sí -- she is
tá muid -- we are ... or ... táimid
tá sibh -- y'all are
tá siad -- they are

Examples:
Tá mé anseo anois -- I am here now
Tá Seán ag rith -- Seán is running
Tá sí ina seasamh -- She is standing (literally, in her standing)

Bí is irregular in the immediate present tense, meaning that when a helper word is used (ní, an, nach, go, etc) the root changes -- in this case from tá to fuil. Remember that ní lenites the following verb -- ní + fuil >> ní fhuil. Also remember that fh is silent and so 'ní fhuil' sounds like 'níl', which is how this is written now, and has been written for several hundred years. A dialectical variant to ní is chan, which would be written chan fhuil.

níl mé -- I am not ... or ... nílim
níl tú -- you are not
níl sé -- he is not
níl muid -- we are not ... or ... nílimid
níl sibh -- y'all are not
níl siad -- they are not

Examples:
Níl mé thuas an staighre -- I am not upstairs
Níl Seán ag siúl -- Seán is not walking
Níl sí go deas -- She is not nice

The helper word an creates the question and eclipses the following verb -- in this case fuil -- an + fuil >> an bhfuil.
an bhfuil mé? -- am I? ... or ... an bhfuilim?
an bhfuil tú? -- are you?
an bhfuil sé? -- is he?
an bhfuil sí? -- is she?
an bhfuil muid? -- are we? ... or ... an bhfuilimid?
an bhfuil sibh? -- are y'all?
an bhfuil siad? -- are they?

Examples:
An bhfuil mé sa rang ceart? -- Am I in the correct class?
An bhfuil Seán ag leamh? -- Is Seán reading?
An bhfuil sí ard? -- Is she tall?

The helper word nach creates the negative question and eclipses the following verb -- in this case fuil -- so nach + fuil >> nach bhfuil.

nach bhfuil mé? -- am I not? ... or ... nach bhfuilim?
nach bhfuil tú? -- aren't you?
nach bhfuil sé? -- isn't he?
nach bhfuil sí? -- isn't she?
nach bhfuil muid? -- aren't we? ... or ... nach bhfuilimid?
nach bhfuil sibh? -- aren't y'all?
nach bhfuil siad? -- aren't they?

Notice that except for the first-person forms, all other persons use the exact same form as the third person. From now on, in order to save space, I will only show a form if it is different from the third-person form.