1) the smallest unit of a chemical element (atom)

2) the smallest amount of (least)

3) a line or point that may not or cannot be passed; greatest or smallest amount, extent etc of what is possible (limit)

4) smallest in amount or degree (minimal)

5) to reduce (something) to the smallest amount or degree (minimize)

6) of the smallest possible (minimum)

7) the smallest unit (usually a group of atoms) into which a substance can be divided without a change in its chemical nature (molecule)

8) the smallest meaningful part into which a word can be divided (morpheme)

9) fastened, fixed, fitting or held closely; stretched fully; (especially in compounds) made so that something cannot get out or in; packed so as to occupy the smallest possible space or to get in as much as possible (tight)