(simile) very simple, easy as pie

a one-way trip / a one-way ticket

(grammar) simple future (verb tense)

(derogatory) daft, simple-minded

in one's birthday suit, naked as a jaybird, in all one's glory

(grammar) simple sentence

single-entry

Alternative form of dans le plus simple appareil

elementary substance

(transitive) to reduce to its simplest form, to its simplest terms; to reduce to the bare minimum