S: (n) form, variant, strain, var. ((biology) a group of organisms within a species that differ in trivial ways from similar groups) "a new strain of microorganisms"
W: (v) vary [Related to: variate] (be subject to change in accordance with a variable) "Prices vary"; "His moods vary depending on the weather"
S: (n) version, variant, variation, edition (something a little different from others of the same type) "an experimental version of the night fighter"; "a variant of the same word"; "an emery wheel is the modern variation of a grindstone"; "the boy is a younger edition of his father"