The verb catch

1) catch a virus — literal/medical (or literal for computers)

• Meaning: to become infected with a virus (biological or computer).

• Grammar: catch + a/an + virus (direct object).

• Example: I caught a virus last week and had to stay home. (Ich habe letzte Woche ein Virus bekommen und musste zu Hause bleiben.)

• Notes: Can be used metaphorically for computers: My laptop caught a virus. (Mein Laptop hat sich einen Virus eingefangen.)

2) catch on — phrasal verb (different senses)

• Meaning A (become popular): to become fashionable or widely accepted.

  • Example: That song really caught on this summer. (Dieses Lied wurde diesen Sommer richtig beliebt.)

• Meaning B (understand): informal — to understand or realize something (often catch on to).

  • Example: She didn’t catch on until I explained it twice. (Sie hat es erst verstanden, nachdem ich es zweimal erklärt habe.)

  • Example with to: He caught on to the trick quickly. (Er hat den Trick schnell durchschaut.)

• Grammar: intransitive (no direct object) for “become popular” / often followed by to + object for “understand.”

• Register: informal to neutral.

Quick contrast sentences:

• I caught a virus, so I couldn’t go out. (Ich habe mir ein Virus eingefangen, also konnte ich nicht raus.) — medical, physical effect.

• The new app caught on fast — everyone’s using it. (Die neue App wurde schnell populär — jeder benutzt sie.) — popularity.

• It took him a while to catch on to the plan. (Er hat eine Weile gebraucht, um den Plan zu verstehen.) — comprehension.

Synonyms:

• catch a virus → get infected, contract a virus (more formal).

• catch on → (popular) take off, become trendy; (understand) get it, figure out.

🔹 Common literal uses

• catch a ball / train / bus / flight → grab / be in time for.

  • He caught the train at 8:15.

• catch a fish / rabbit / thief → capture physically.

  • They caught the thief red-handed.

• catch a cold / disease / virus → become ill.

  • She caught a cold in the rain.

• catch someone’s eye → attract attention.

  • That painting really caught my eye.

• catch fire → start burning.

  • The old barn caught fire last night.

🔹 Idiomatic phrasal verbs

• catch on (to sth.) → understand / become popular.

• catch up (with sb./sth.) → reach same level / speed.

  • I’ll catch up with you later.

• catch out (sb.) → trick or expose.

  • The teacher caught him out in a lie.

• catch at (sth.) → grab quickly (old-fashioned, literary).

  • She caught at his sleeve.

• catch up in → become involved, often unwillingly.

  • He was caught up in the scandal.

• catch onto → informal = understand.

  • She finally caught onto the rules.

🔹 Figurative set phrases

• catch someone off guard → surprise.

• catch someone’s breath → pause to recover.

• catch someone in the act → witness wrongdoing.

• catch someone by surprise → unexpected.

• catch someone’s attention → draw focus.

• catch a glimpse of → see briefly.

• catch someone’s imagination → inspire.

👉 Notice:

• When catch is followed by a noun (virus, train, ball), it usually means take, capture, grasp, or get.

• When it’s part of a phrasal verb (catch on, catch up, catch out), the meaning is often idiomatic and not literal.