Four words have been given, out of which three are alike in some manner and one is different. Select the odd one.

Let's analyze all the options:

(a) Degree → A qualification awarded after completing a course of study.
(b) College → An educational institution offering higher education.
(c) Polytechnic → An institution providing technical education.
(d) School → An institution for primary or secondary education.
Odd One:
College, Polytechnic, and School are all educational institutions. 
Degree is not an institution but a qualification. 
Therefore, Degree is the odd one out.
Thus, the correct option is (a) Degree.