ことだし

ことだし gives a reason that makes a decision or a suggestion easy: "since", "seeing as", "now that". It follows a plain-form verb or an い-adjective, and the second half is usually "let's", "shall we", or what the speaker has decided or concluded.

It belongs to conversation, and it is softer than から or ので. The reason is offered as one of several, the way きごう〜し lists reasons, and it tips the balance. せっかく and もう often open the first half.

Not for plain cause and effect

ことだし leads to what the speaker wants, proposes or judges. A result that simply followed, with nobody choosing it, takes ので or から.

• × 雨が降ったことだし、試合は中止になった → 雨が降ったので、試合は中止になった

Usage notes

These go beyond a reason after a verb or an adjective.

のことだし with a person

After a person and の, ことだし bases a guess on what you know of them, like のことだから but more casual.

な-adjectives

A な-adjective keeps its な before ことだし.