pattern - What is a Single Word™?

_{This is in the spirit of the What is a Word/Phrase™ series started by JLee with a special brand of Phrase™ and Word™ puzzles.}

If a word conforms to a special rule, I call it a Single Word™.

Use the following examples below to find the rule.

And, if you want to analyze, here is a CSV version:

Single Words™, Non Single Words™
water, food
bear, grizzly
beeswax, honey

zebra, horse
deer, buck
rat, mouse
cat, feline
dad, father
mom, mother
you, me

Answer

A Single Words™ looks like one which

Is typed using just one hand with a standard keyboard touch typing method

Left hand letters are Q, W, E, R, T , A, S, D, F, G , Z, X, C, V, B

Right hand letters are Y, U, I, O, P , H, J, K, L , N, M

And the Non Single Words™ need both hands to touch type.