weihnachtlich
Christmassy
Having or spreading the mood, atmosphere, or character of Christmas.
Im ganzen Haus duftete es weihnachtlich nach Plätzchen und Tannennadeln.
The whole house smelled Christmassy, like cookies and pine needles.

Christmassy
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Christmassy
Having or spreading the mood, atmosphere, or character of Christmas.
Im ganzen Haus duftete es weihnachtlich nach Plätzchen und Tannennadeln.
The whole house smelled Christmassy, like cookies and pine needles.

The adjective 'weihnachtlich' (Christmassy) is derived from the noun 'Weihnachten' (Christmas). The ending '-lich' turns the noun into an adjective and means something like 'in the style of Christmas'.
Die weihnachtliche Beleuchtung in der Stadt ist wunderschön.
The Christmassy lights in the city are beautiful.
You can use 'weihnachtlich' before a noun (attributively) or as a description after a verb like 'sein' (to be) or 'wirken' (to seem/appear) (predicatively).
Wir hören weihnachtliche Lieder.
We're listening to Christmassy songs.
The adjective often describes an atmosphere or sensory perception. Common combinations are 'weihnachtliche Stimmung' (Christmassy mood), 'weihnachtliche Dekoration' (Christmas decorations), 'weihnachtliche Musik' (Christmas music), or 'weihnachtlicher Duft' (Christmassy scent).
Überall lag ein weihnachtlicher Duft von Zimt und Orangen in der Luft.
A Christmassy scent of cinnamon and oranges was in the air everywhere.
Christian
'christlich' and 'weihnachtlich' can both have to do with Christmas, but they do not mean the same thing. 'christlich' refers to Christianity, that is, to religion, faith, teachings, or Christian culture. 'weihnachtlich' describes the mood or character of Christmas, for example music, lights, decorations, or smells. Learners may confuse the words because Christmas is a Christian holiday. But a room with lights and the smell of cookies is more likely weihnachtlich, while a prayer or church service is christlich.

Mit den Kerzen und dem Tannenduft wirkt das Wohnzimmer sehr weihnachtlich.
With the candles and the scent of fir, the living room feels very Christmassy.
In der Kirche hören wir ein christliches Lied.
In the church, we hear a Christian song.