This German philosopher bluntly stated that The meaning of a word can only be known in the context of the sentence that contains the word. This is pretty heavy because if one only utters, for example, the term Red outside the structure of a sentence, any English speaker might envision an apple or any other number of red objects.
Phillip Stokes explained what Frege meant with examples like the sentence ( ) is wise upon which the substitution of the Socrates between the parentheses would indicate Socrates is a member of the class of wise entities. Also even, numbers are only given meaning according to Frege in a similar fashion. For example the numbers two and three are given meaning the context of addition , ( ) + ( ) or concretely 2+3=5.
This is all interesting but, I don’t concur that it is the only way for meaning to be conveyed. The red apple example indicates meaning can be acquired empirically not necessarily requiring the structure of a sentence. There is no doubt that words do change their meanings over time and that change is conveyed in the sentences that contains them. However, this is not the only way that meaning can be affixed to a term.