Learn Hardcore Turkish: O bana büyük bir jest yaptı.

bana is the dative form of ben that marks the person receiving or benefiting from the action. Here it means to me or for me. beni is the accusative form (me as a direct object) and would not work because the noun jest is the direct object of yapmak. You could use benim için (for me) as a prepositional phrase, but that construction (possessive pronoun + için) feels a bit more formal and changes the phrasing.

Why is there a bir before jest and why does it come after büyük

In Turkish bir is the indefinite article meaning a or an. When an adjective comes before a noun, bir sits between the adjective and the noun: adjective + bir + noun. So büyük bir jest literally means a big gesture. Without an adjective you would simply say bir jest for a gesture.

Why is the subject pronoun O included and is it mandatory

Subject pronouns such as o (he / she / it) are optional in Turkish because the verb ending already shows the person. You can drop o and still say Bana büyük bir jest yaptı to mean he or she made a big gesture to me. Including o adds emphasis or clarity (for example to contrast with someone else) but it is not required.

What does jest mean and is it related to English

jest in Turkish means a kind or polite gesture, favor, or an act of goodwill. It’s a loanword (from French or Latin) and is similar to the English word gesture, but in Turkish it often refers specifically to a thoughtful or courteous act rather than any simple movement.

How is the past tense yaptı formed and why isn’t it yapdı

The verb yapmak (to do or make) takes the simple past suffix -dı/-di/-du/-dü with vowel harmony. Since the stem ends in the voiceless consonant p, the initial d of the suffix becomes voiceless t by consonant harmony, giving yaptı. There is no extra ending for third person singular, so yaptı by itself means he/she/it did or he/she/it made.

Can we say O bana büyük bir jest etti instead of O bana büyük bir jest yaptı

Yes. Both jest yapmak and jest etmek are used to express doing someone a favor or making a gesture. jest etmek might sound slightly more formal or direct, while jest yapmak is very common in everyday speech. The overall meaning remains the same.

Is the word order fixed here or can we move elements around

Turkish word order is relatively flexible, though the neutral pattern is subject + indirect object + direct object + verb. You can omit o and start with bana for focus (Bana büyük bir jest yaptı). You could also say O büyük bir jest bana yaptı or Büyük bir jest yaptı bana to emphasize a different part of the sentence. The verb typically stays at the end.

Does büyük always mean physically large or can it be figurative

While büyük literally means big or large, it is commonly used figuratively to mean great or significant. In büyük bir jest it conveys a great or generous gesture rather than a gesture of large size.

Why is jest not plural here; could we say jestler

Here the speaker refers to a single act of kindness, so jest is singular. If you wanted to talk about multiple gestures, you would pluralize it: O bana büyük jestler yaptı means he/she made big gestures for me (more than one).

Could I use benim için instead of bana, and if so how

Yes. benim için means for me and combines the possessive pronoun -im with the postposition için. You can say O benim için büyük bir jest yaptı, which carries the same meaning but registers as slightly more formal.