An ASL learner asked for an explanation on how concepts are expressed in American Sign Language (ASL), using the preposition "for" in English. Below is a few sentences that are translated into ASL with explanation. The preposition "for" is used in ASL, but not all is expressed the same.
Gloss: me/i will 2h-do anything for hir.
English translation: I would do anything for him.
The preposition for is used in this ASL sentence. It is used to indicate what the person would do for (who).
Gloss: i buy gift for my brother.
English translation: I bought a gift for my brother.
The preposition for is used in ASL to indicate what the gift is for (who).
The gloss buy in the ASL sentence above does not mean the present tense. Usually, the signer indicates a tense (e.g. "yesterday", "last-week", "tomorrow", "in-past", etc" in a sentence). Glossing only provides an approximate "translation" of a morpheme (word). Note that the ASL word gift also can be fingerspelled by some signers.
Gloss: i fight "want" free(dom).
English translation: I'm fighting for freedom.
This one is different from the others above. The person is fighting, not doing something for freedom (as if a person) but fighting to get freedom for oneself. Thus, the signed for in replacement of "want" would be somehow awkward and somehow incorrect.
Another example similar to this is: i fight/dispute want money #back. In this sense, the English translation would be this: I'm fighting for the refund. The signed fight/dispute (as in "an intense verbal dispute) is different from the above. The word fight in English is the same but semantic or meaning is different; thus, the ASL sign is different. Like any foreign language, translation is not done by word for word but by concept or meaning.
Related tutorial: prepositions INTO and IN in sign language.