sonderbar
strange
Deviating from the norm in a strange, odd, or unexpected way; unfamiliar or peculiar.
Er hat die sonderbare Angewohnheit, im Sommer einen Wollschal zu tragen.
He has the strange habit of wearing a wool scarf in the summer.

strange
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strange
Deviating from the norm in a strange, odd, or unexpected way; unfamiliar or peculiar.
Er hat die sonderbare Angewohnheit, im Sommer einen Wollschal zu tragen.
He has the strange habit of wearing a wool scarf in the summer.

The word consists of the stem 'sonder' and the ending '-bar'. The stem 'sonder' is related to 'besonders' (special) and means 'separate' or 'special'. So 'sonderbar' (strange) describes something that is separate from the norm.
Er hat einen recht sonderbaren Geschmack, was Kleidung angeht.
He has rather strange taste when it comes to clothing.
'Sonderbar' (strange) is often used to describe behavior, habits, or people. Common combinations are 'ein sonderbarer Mensch' (a strange person), 'eine sonderbare Angewohnheit' (a strange habit), or the verb phrase 'sich sonderbar verhalten' (to behave strangely).
Nach dem Vorfall hat er sich sehr sonderbar verhalten.
After the incident, he behaved very strangely.
'Sonderbar' (strange) belongs more to written language or a somewhat elevated style. It can sometimes sound slightly old-fashioned or more formal.
In dem alten Buch wurde die Geschichte auf eine sonderbare Weise erzählt.
In the old book, the story was told in a strange way.
especially / special
'besonders' and 'sonderbar' sound similar, and both can express that something is not completely ordinary. But the difference is important: 'besonders' is often positive or neutral and means 'special', 'especially', or 'extraordinary'. 'sonderbar', on the other hand, means 'strange' or 'odd' and often has a slightly negative or uncertain tone. So you can say that a day is 'besonders schön' (especially beautiful), but not 'sonderbar schön'. 'sonderbar' fits when something seems odd or is not as expected.

Nach dem Telefonat war seine Stimme plötzlich sonderbar ruhig.
After the phone call, his voice suddenly sounded strangely calm.
Der Kuchen schmeckt heute besonders gut.
The cake tastes especially good today.