noun
postage stamp, stamp
A1
Briefmarke is a feminine noun meaning 'postage stamp' or simply 'stamp'. Plural is Briefmarken. Declension: die Briefmarke (sg.), die Briefmarken (pl.). It’s used for postage on letters and postcards. No irregular plural or special preposition; just a basic concrete noun in postal contexts.
Examples
Auf den Brief klebe ich eine Briefmarke.
I'll stick a postage stamp on the letter.
Für diesen Brief brauchst du eine Briefmarke.
You need a stamp for this letter.
Hast du eine Briefmarke für die Postkarte?
Do you have a stamp for the postcard?
Details
Mnemonics
Picture a small mark (stamp) stuck to an envelope
Die Briefmarke — think 'the mark on the brief' to remember feminine 'die'.
Notes
Always used for postage; plural is irregular (Briefmarken).