Das Verb „sinn“ (sein) im Präsens

Sinn means "to be", and like English "be" it is irregular: am, are, is have nothing in common, and neither do sinn, bass, ass.

Person	Form	Example
ech	sinn	Ech sinn doheem. - I'm at home.
du	bass	Du bass midd. - You're tired.
hien / si / hatt	ass	D'Gëlle Fra ass an der Stad. - The Gëlle Fra is in the city.
mir	sinn	Mir sinn aus Esch. - We're from Esch.
dir / Dir	sidd	Dir sidd wëllkomm. - You're welcome (to come).
si	sinn	Si sinn aus Portugal. - They're from Portugal.

Three persons share one form, sinn, so the pronoun does the work: ech sinn, mir sinn, si sinn.

sinn or si?

You will see both spellings, and both are correct. Sinn keeps its -n before a vowel and before n, d, t, z, h; before any other consonant it loses it: Ech sinn aus Lëtzebuerg, but Ech si midd and Mir si Lëtzebuerger - we're Luxembourgers. This is the n-rule (Eifeler Regel), and the spelling follows the sound.

Where English and Luxembourgish part ways

• There is no "-ing" form. "I am eating" is simply Ech iessen; Ech sinn amgaang ze iessen exists for "I'm busy eating", but it is the marked choice. Do not build *Ech sinn iessen.
• Being cold or warm is said with mir (to me), not with ech: Mir ass kal - I'm cold. Ech si kal would describe your personality.
• Sinn also forms the past of verbs of movement: Ech si komm - I came / I have come.