soujiki o kakenai to, heya no kaapetto ga sugu ni yogoremasu.

If I don’t use the vacuum cleaner, the carpet in the room quickly gets dirty.

Breakdown of soujiki o kakenai to, heya no kaapetto ga sugu ni yogoremasu.

• が: subject particle
• の: possessive case particle
• と: conditional particle
• 部屋へや: room

Questions & Answers about soujiki o kakenai to, heya no kaapetto ga sugu ni yogoremasu.

Why does 掃除機 go with をかける? I thought かける means “to hang” or “to put on the phone,” etc.

掃除機をかける is a fixed expression that means “to vacuum (a room, carpet, etc.)”.

The verb かける has many meanings like “to hang,” “to apply,” “to put on,” “to make (a phone call),” etc. In this expression, the idea is roughly “to run/apply the vacuum over (the floor, carpet, etc.)”.

Similar patterns:

• アイロンをかける – to iron (clothes)
• クリームを顔にかける – to put/apply cream on your face
• ブラシをかける – to brush (e.g., hair, clothes)

You could say 掃除機を使う (“use a vacuum cleaner”), but when you mean “vacuum the carpet/floor,” 掃除機をかける sounds the most natural.

What exactly does 〜ないと mean here in 掃除機をかけないと? Is something left out?

In this sentence, 〜ないと is a shortened form of a conditional pattern:

• (掃除機を) かけないと、部屋のカーペットがすぐに汚れます。
  → “If (you) don’t vacuum, the carpet gets dirty quickly.”

Here ないと is literally “if (you) don’t …”, with と as the conditional particle (“if/when”).

There is another, related use where 〜ないと is short for:

• 〜ないといけない / 〜ないとだめだ / 〜ないと困る
  → “have to ~ / must ~”

Example:

• 早く寝ないと。
  (short for 早く寝ないといけない.)
  → “I have to go to bed early.”

In your sentence, though, because it is followed by a consequence (カーペットが汚れます), ないと is understood simply as “if you don’t …”, not “you must …”.

What is the role of in ? How is this different from using or ?