psi / scye / scythe / sie / sigh are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
psi: (noun) the 23rd letter of the Greek alphabet.
scye: NA
scythe: (noun) an edge tool for cutting grass; has a long handle that must be held with both hands and a curved blade that moves parallel to the ground. (verb) cut with a scythe.
sie: NA
sigh: (noun) an utterance made by exhaling audibly. (noun) a sound like a person sighing. (verb) heave or utter a sigh; breathe deeply and heavily. (verb) utter with a sigh.
psi: s·AY
scye: NA
scythe: s·IH·th
sie: s·IY
sigh: s·AY
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)