"The Klingon is a child."
Translation:puq ghaH tlhIngan'e'.
ghaH is for "beings capable of language". 'oH is for things that are not beings or are not capable of language". In this case, the Klingon is a "being capable of language", so you use ghaH.
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It is a grammatical marker that does not exactly match anything we have in English, so there is no direct translation for it. There is a way to express it in an English sentence, but I'll get to that in a minute. Let me first explain why it is required in this sentence.
Since the pronoun in a “pronoun as the verb to-be” sentence is acting as both the verb and the subject, it is not possible to put a separate subject also in the sentence to explain who or what the pronoun is actually referring to. SuvwI' ghaH means, “He is a warrior.” SuvwI' ghaH tera'ngan is ungrammatical since the ghaH and the tera'ngan are both trying to be the subject and you cannot have both at the same time in Klingon. So instead we mark the noun as the “topic” in Klingon with the marker -’e’ and place that “topic” in the subject position to help make the connection. This is a very special grammatical construction and is absolutely required when trying to use an explicitly stated subject with a “pronoun as the verb to-be”. Since the noun with -'e' is grammatically acting as the “topic” and not the subject, it can be translated with, “As for ..., he is ...”
So this sentence can be translated by saying, "As for the Terran, he is a warrior," but it is the Klingon equivalent of saying, "The Terran is a warrior."