Scroll down to the bottom of this link http://www.bitesizeirishgaelic.com/blog/i-me-he-him/ for the emphatic forms of le+ pronoun.
In general, though, be prepared to see a -se (mise), -sa (tusa), etc (complete list:http://nualeargais.ie/gnag/person.htm) to put emphasis on a pronoun instead of saying the word more forcefully. The preposition + pronoun construction often has special forms, too, like liomsa and leatsa.
I think it's leatsa because of the implied contrast: i.e. it's yours (not mine / not hers / etc.). Think of the "tune" of an English sentence like "The lobster's mine but the crab's yours"; how it emphasizes the last word. This is done in Irish with the addition of an "emphatic particle", -sa.
I'd say that is leat is more likely to be used where the emphasis is more on the "what" than the "whose" -- especially in a list. The only example I can think of for the moment is from the Bible, Psalm 47: The day is thine, the night also is thine = Is leat an lá agus is leat an oíche.
This was such a wonderful explanation!!! Thank you for the link, Cait48!
That depends on the sentence. The sentence I see on the page is Is leatsa an portán In this case, bportán would not be possible, since the article an (the) doesn't change masculine nouns like portán. If you had a sentence where you wanted to say your crab--like Your crab is on the table, you could say do phortán (to one person) or bhur bportán (to two or more people).
An identificational copular statement with a third-person pronoun as the subject can’t have the copula directly adjacent to its complement; the first é is a “subcomplement” that provides that separation. Think of it as approximately “It’s that, your crab.”, with the first é corresponding (non-literally) to “that”.
I'm not a native speaker, and very far from becoming fluent - but, with due respect, I don't find the phrase awkward- you'll find the rhythm echoed in some dialects ( if that helps) - "it's your crab (so) it is" - " it's your crab, hey." I found this helped me a bit when trying to get my head round some of the constructions and how they might be varied.
Is é is commonly contracted to sé so you might hear Sé do phortán é.
There is an Irish song whose chorus begins Sé mo laoch mo ghile mear.
That is the normal structure for an identificational copular statement with a third-person pronoun as the subject, so that’s how I’d use it. I’m not a native Irish speaker, though, so you’ll need to find some to ask to find out if they’d shorten it — my guess is that a native speaker would probably pronounce it as ’Sé do phortán é.
It's an archaic second-person singular possessive--in other words, 'your.' In theory, 'thy' was used before consonants and 'thine' before vowels. Shakespeare wrote (in that famously misunderstood line from Hamlet), 'To thine own self be true.'
Where did this question come from? I find some of Duolingo's sentences unnatural, but not to the extent of using 'thine'!
Thou, thee, thine, old forms for second person still found in prayers: Our Father, Who art in Heaven, hallowed be Thy name; Thy Kingdom come, Thy will be done on earth as it is in Heaven.
Differently from what?
Portán is the basic form, the one you would find in a dictionary. Sometimes (like after mo and do) there is a séimhiú on the word, which is then spelled phortán. At other times (like after ár or bhur) there is an urú on the word, which is then spelled bportán.
It is all explained in the notes we may read at the beginning of each new topic.
Because Is le X an Y is how you say "the Y is Xs".
Is le Pól é - "it is Pauls"
Is liomsa é - "it is mine"
is leatsa é - "it is yours"
is leisean é - "it is his"
Is linne e - "it is ours"
Is le Pól an portán - "ithe crab is Pauls"
is liomsa an portán - "the crab is mine"
is leatsa an portán - "the crab is yours"
is leisean an portán - "the crab is his"
is linne an portán - "the crab is ours"
Is é an portán an cheann s'agatsa is one way that you might say "yours is the crab"
There are some general rules about determining gender of nouns, but I don't know what/if Duolingo teaches you anything about that. Failing any sort of instruction on that, you can look up a word in a dictionary. The dictionary will tell you the gender of the noun. https://www.teanglann.ie/en/fgb/port%C3%A1n
However, the sentence asks for 'the crab.' Even if you had a feminine noun in this sentence, you wouldn't add a b. The crab is yours --> Is leatsa an portán. (Portán is masculine.) The blanket is yours --> Is leatsa an phluid. (Pluid is feminine.)