This is the 77th most frequent Arabic word.
فقط
Only.
The word 'فقط' is used here to denote exclusivity, emphasizing that only vegetables are eaten, and not anything else.
أنا آكل فقط الخضروات.
I eat only vegetables.
Here, 'فقط' serves to emphasize that viewing the paintings was the sole purpose of going to the museum.
ذهبت إلى المتحف فقط لرؤية اللوحات.
I went to the museum only to see the paintings.
In this sentence, 'فقط' emphasizes the condition under which the subject likes books, specifically that they must be interesting.