
lau
mild
A temperature that is pleasantly warm but not hot; lukewarm.
An einem lauen Sommerabend saßen wir noch lange draußen.
On a mild summer evening, we sat outside for a long time.
mild / lukewarm
Loading your saved state.

mild
A temperature that is pleasantly warm but not hot; lukewarm.
An einem lauen Sommerabend saßen wir noch lange draußen.
On a mild summer evening, we sat outside for a long time.

lukewarm
Figuratively, for something that happens without much interest, enthusiasm, or commitment; half-hearted.
Nach der enttäuschenden Vorstellung gab es nur lauen Applaus.
After the disappointing performance, there was only lukewarm applause.
You can tell whether the literal or figurative meaning is intended from the noun. If 'lau' refers to the temperature of air or water, it is meant literally. If it refers to a human reaction such as applause or interest, it is figurative.
Ein laues Lüftchen wehte vom Meer her.
A mild breeze blew in from the sea.
In the literal meaning, 'lau' (mild/lukewarm) is often used positively and poetically for pleasant temperatures. Especially common are the combinations 'ein lauer Sommerabend' (a mild summer evening) or 'ein laues Lüftchen' (a mild breeze).
Wir genossen die laue Nacht auf dem Balkon.
We enjoyed the mild night on the balcony.
In the figurative meaning, 'lau' (lukewarm) describes a lack of enthusiasm and has a negative connotation. Typical combinations are 'lauer Applaus' (lukewarm applause), 'eine laue Reaktion' (a lukewarm reaction), or 'laues Interesse' (lukewarm interest).
Die Reaktion des Publikums auf den Film war eher lau.
The audience's reaction to the film was rather lukewarm.
weak / matte
Matt and lau can initially seem similar when describing a weak effect. Matt mainly describes physical lack of strength, while lau refers to little interest or half-hearted commitment. When referring to someone’s own condition, matt is appropriate; when referring to a lack of enthusiasm for something, lau is appropriate.

Bei der langen Besprechung zeigte Anna nur laues Interesse und beteiligte sich kaum.
During the long meeting, Anna showed only lukewarm interest and barely participated.
Nach der langen Besprechung fühlte sich Anna körperlich matt und ohne Energie.
After the long meeting, Anna felt physically weak and had no energy.