understanding, comprehension / appreciation

(set theory) a Venn diagram

to use / to employ / to make use of, to apply / to spend

vision; sense of sight

understand, comprehend / appreciate

gathering, assembly / an assortment / (mathematics) set

relationship, relation / involvement, participation / personal connection, family relationship / romantic relationship

be related / be romantically involved

gather, assemble, aggregate

a target, a mark, a bullseye / an objective, an object (of doing something)