To make an affirmative answer to a question in Irish, you repeat the verb. If the question involves the copula, like An póilín tú? - "Are you a policeman?", the affirmative answer is Is ea or 'Sea. If the question is An bhfuil ....? the answer is Tá, if the question is an raibh ....? the answer is bhí, if the question is An ólann tú caife?, the answer is Ólann, etc.
This doesn't come naturally to English speakers, who are used to using "Yes" to answer any type of question.
If you are responding to a question that uses the copula, then you have to use the copula in the answer - An lá fuar é? "is it a cold day?" - Is ea "It is".
If the question doesn't use the copula, and uses the verb bí instead then you use tá sé as the answer - An bhfuil sé fuar? "Is it cold?" - Tá sé "It is"
Notes: an bhfuil is interrogative form of bí in the present tense.
You don't need to include the sé in this case - just tá is sufficient.
(If you don't understand when the copula is used yet, don't worry, it'll get easier with practice, but using the verb bi when you should use the copula is a frequent mistake for beginners.
'S ea or an ea with the copula, tá with bí. That's clear. But what about with other verbs? I would welcome any clarification. For example. "An léann tú ar maidin? Léim." Is it legitimate, instead of léim to answer with 'S ea? I'm guessing not, but it would be good to be clear on this point.
So, if I understand the situation, the "s" is normally broad in the word "is" regardless of its slender environment but reverts to its proper slender state in certain fixed expressions such as "is ea". Right? By this assumption, I tend to conclude that historically, "is" was at one time [ıʃ]. ??
As this is an Irish to English exercise, i presume you are saying that Sea should be accepted for a "Type what you hear" exercise?
Apart from the fact that she very clearly says Is ea rather that 'S ea, there is no facility for "alternative translations" for this type of question (it's not a translation exercise) and these exercises are really "Type what she said" exercises, because they were designed for a text-to-speech "speaker", where "she" always reads the script, and your answer is compared to the script.
That's correct, this is a 'Type what you hear' exercise. An instructive mistake, because I hadn't heard the vowel. To my ear it's very soft. Also maybe expectation played a role, since I'd been given to understand that copula ' Is' is frequently reduced to /s/. Guess not as often as I'd supposed. Thanks!
is ea is always pronounced with a slender s, and is often reduced down to just 'S ea, often written Sea. Usually, even, but not always. The same thing happens for is é and is í.
But in this case, the i is audible. You can listen to the audio here - depending on your web browser, you may be able to right-click on the player to change the playback speed.