This is the 13969th most frequent Turkish word.
mektubunda
"In his/her letter."
The word 'mektubunda' means 'in your/her/his letter' and is a possessive construction ('mektubu') combined with a locative case suffix ('-nda'), indicating inclusion or location within the letter.
Selin, mektubunda güzel anılarını paylaştı.
Selin shared her beautiful memories in her letter.
Here, 'mektubunda' similarly means 'in your/her/his letter,' but the context focuses on the contents addressed to Ali.
Ali'ye mektubunda neler yazdığını merak ettim.
I wondered what you wrote in your letter to Ali.
In this sentence, 'mektubunda' again highlights the concept of being in a letter, reflecting its possessive and locative grammatical use.