ついでに— While You're At It

• 買い物のついでに、郵便局に寄った。

  Kaimono no tsuide ni, yuubinkyoku ni yotta.

  While out shopping, I dropped by the post office.

  Noun 買い物 + の + ついでに makes the post office stop an add-on to shopping.

• 散歩するついでに、パンを買ってきて。

  Sanpo suru tsuide ni, pan wo katte kite.

  While you're out for a walk, buy some bread.

  Verb plain form 散歩する + ついでに tacks buying bread onto the walk.

• 出張のついでに、実家に顔を出した。

  Shucchou no tsuide ni, jikka ni kao wo dashita.

  While on the business trip, I stopped by my parents' home.

  Noun 出張 + の + ついでに frames the visit as convenient to the main trip.

• ・The main action is the real purpose; the ついでに action just fits in conveniently.
• ・With nouns, insert の (買い物のついでに).
• ・Register: neutral; extremely common in daily speech.

Commonly confused with

The JLPT rarely asks whether you recognise a pattern — it asks which of several similar patterns fits. These are the ones ついでに is tested against.

• ～一方(で) — On One Hand, On the Other
• ～上(に) — On Top of That
• ～くせに — And Yet You Dare
• だけでなく — Not Only That
• ～つつ(も) — While Yet Doing Otherwise
• ～というと／～といえば — Speaking Of That
• ～といっても — Even Though I Say
• ～とともに — Along With, As