eineinhalb
one and a half
Refers to the number 1.5; one plus half of one.
Der Film dauert eineinhalb Stunden.
The film lasts one and a half hours.

one and a half
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one and a half
Refers to the number 1.5; one plus half of one.
Der Film dauert eineinhalb Stunden.
The film lasts one and a half hours.

The word 'eineinhalb' (one and a half) is made up of 'ein', 'ein', and 'halb'. This pattern also works for other numbers, for example 'zweieinhalb' (2.5) or 'dreieinhalb' (3.5).
Die Wanderung dauerte zweieinhalb Stunden.
The hike lasted two and a half hours.
Although the word begins with 'ein-', the following noun is always plural. So it is 'eineinhalb Stunden' (one and a half hours), not 'eineinhalb Stunde'.
Ich warte schon seit eineinhalb Stunden auf den Bus.
I've been waiting for the bus for one and a half hours already.
The numeral 'eineinhalb' (one and a half) is not declined. It always keeps its basic form, regardless of which case it is in.
Nach eineinhalb Jahren in Deutschland spricht sie fließend Deutsch.
After one and a half years in Germany, she speaks fluent German.
one and a half
'anderthalb' and 'eineinhalb' mean the same thing: 1.5. You can use both before nouns, for example with time, amounts, or distances. 'eineinhalb' is easier for many learners to understand because you can directly hear 'ein' and 'halb'. 'anderthalb' is shorter and also completely normal, but it can be confusing at first because it does not look like 'eins und halb'. So the words are interchangeable. The important point is simply: both mean exactly one plus one half, not two.

Für den Kuchen braucht Sofia eineinhalb Tassen Milch.
Sofia needs one and a half cups of milk for the cake.
Ich warte seit anderthalb Stunden auf den Bus.
I have been waiting for the bus for one and a half hours.