To AhmedElkas19: כנסת by itself means assembly. So for the Knesset I think you would mostly see הכנסת. When you have בית הכנסת it means the house of assembly or more commonly, the synagogue. The word synagogue is from a Greek word also meaning meeting place. Google defines it as, "from Greek sunagōgē ‘meeting,’ from sun- ‘together’ + agein ‘bring.’"
thank you so much .but I took the word from duolingo recommendation tips not from google translate
Because this is a construct state: when you add "ה" (as "the") to a construct state it's always to the second of the two word. So for example:
Birthday - יום הולדת
The birthday - יום ההולדת
To the birthday - ליום ההולדת
I heard that in colloquial use the definite article is sometimes appended to the first word and not the second. How true is that?
Oh, it's quite common, more often with the most used constructs (יום-הולדת, בית-ספר, בית-כנסת, בן-אדם etc.). I think "הבן אדם" for example is much more common than "בן האדם", and some people even write "בצפר" or "יומולדת" (though this is especially prevalent online).