רָזֶה, דַּק
When speaking about a person, the word for thin is רָזֶה
for a male, and רָזָה
for a female.
For example:
הִיא עָשְׂתָה דִּיאֶטָה וְעַכְשָׁיו הִיא מְאֹד רָזָה.
She went on a diet and now she is very thin.
When speaking about an object, however, the word is דַּק
for something masculine and דַּקָּה
for something feminine.
For example:
זֶה לֹא סֶפֶר דַּק בִּמְיֻחָד.
It’s not a particularly thin book.
So we’ve covered people and objects. What about animals? There, Modern and Biblical Hebrew are divided. While in Modern Hebrew animals are רָזִים
and רָזוֹת
, in Biblical they are דַּקִּים
and דַּקּות 
Minutes are also called דקות because they are slivers of time.