It states "an" is still translated as "the," should the translation be "Is it the crab?" This one confused me :P
"An" here is actually a question particle corresponding to the English "Is?"
why wouldn't it be. 'An é an portán é? is ea.' instead of your translation of 'is it the crab? it is'
Because "Is ea" means "It is" only for indefinite nouns. "The crab" being definite uses "Is é". ("Is í" if the noun were feminine)
shouldn't it be "An bportán é?"? Since the "an" as question particle triggers eclipsis? Or it does only in verbs?
Great question! The short answer is that the copula is an awkward verb and it ignores the normal rules. The basic sentence would be Is portán é, "It is a crab." To make this a question you swap the "is" for the question particle "an", but you do not add eclipsis.
I think it only applies to "an" as a definite article, not as a question particle. So in AnLonDubhBeag's example above, the translation of "Is it the crab?" should be: An é an bportán é?
No, it applies to the question particle, not the definite article (it lenites feminine). The thing here is that an isn't modifying the verb (which would cause eclipse) but is the question form of the verb.
Technically, ea is a neuter pronoun. Modern Irish doesn't have neuter nouns, but we still use this one pronoun in certain sentences with the copula is.