(and) so
because
since
Structure
Verb + ことだし
［い］Adjective + ことだし
［な］Adjective + な(1) + ことだし
Noun + の(1) + ことだし(1) である
(A) ことだし (B) is an expression used to state reason/cause, implying that there are other reasons as well. It originates in particle し, but it shows the intention to state the reason more clearly as it is not used to simply connect clauses. It is also considered more objective and therefore polite. ことだし often indicates good circumstances (A) to do (B), therefore is followed with expressions of determination, suggestion or invitation like ないか、volitional form、たらどう. When (A) is a noun denoting a person it indicates judgment that based on the person’s character/behavior something is the case.