When do you use a slash mark?

Use a slash

to clarify a relationship in which a hyphenated compound is used.

to separate numerator from denominator

to indicate per to separate units of measurement accompanied by a numerical value

to set off English phonemes.

to cite an unpublished work.

when a phrase would be clearer

Each child handed the ball to her mother or guardian.
not
Each child handed the ball to her mother/guardian.

for simple comparisons. Use a hyphen or short dash (en dash) instead.

more than once to express compound units. Use centered dots and parentheses as needed to prevent ambiguity.