This is the 4037th most frequent Arabic word.
ثلاثين
"ثلاثين" means "thirty" in English.
ثلاثين is used in a counting context to indicate the number thirty.
اشتريت ثلاثين كتابًا.
I bought thirty books.
ثلاثين is used to indicate the age of a person here.
عمري ثلاثين عامًا.
I am thirty years old.
ثلاثين is used to indicate a duration of time in this sentence.