mochikomi wa kanou da.

Bringing food or drink from outside is possible.

Breakdown of mochikomi wa kanou da.

• は: topic particle
• だ: to be
• 可能かのう: possible
• 持もち込こみ: bringing in food or drink

Questions & Answers about mochikomi wa kanou da.

What does 持ち込み mean here, and why is it not 持ち込む?

持ち込み is a noun form derived from the verb 持ち込む, which means to bring in or to bring something into a place.

In this sentence, 持ち込み means something like:

• bringing in outside items
• bringing your own food/drink/items
• outside items being brought in

Japanese often turns verbs into noun-like forms this way. So instead of saying the action as a verb, it treats it as a concept or category.

• 持ち込む = to bring in
• 持ち込み = bringing in / carry-in / outside food and drink, depending on context

So 持ち込みは可能だ is literally closer to As for bringing things in, it is possible.

How is 持ち込み formed from 持ち込む?

It is the ます-stem form of the verb:

• dictionary form: 持ち込む
• polite form: 持ち込みます
• stem: 持ち込み

This stem can often act like a noun.

Examples of the same pattern:

• 読み from 読む = reading
• 休み from 休む = rest / holiday
• 申し込み from 申し込む = application

So here, 持ち込み is a noun-like expression meaning bringing in.