First and Preliminary

First adjective - Coming before all others in time or order.

Preliminary and first are semantically related In some cases you can use "Preliminary" instead the word "First" as an adjective or a noun.

Nearby Word: firstly

Preliminary adjective - Coming before the main part or item usually to introduce or prepare for what follows.

First and preliminary are semantically related in introductory topic. Sometimes you can use "First" instead the word "Preliminary" as an adjective or a noun.