Explanation
Not necessarily; not always.
Formation
必ずしも + Statement + とは限らない
Detailed explanation
The 必ずしも～とは限らない grammar point is used to express that something is not necessarily or not always the case, indicating that a certain assumption may not hold true in all situations.
Examples
Takai mono ga kanarazushimo yoi to wa kagiranai.
Expensive things are not necessarily better.
Yuumei na hito ga kanarazushimo shiawase to wa kagiranai.
Famous people are not necessarily happy.
Gaikokugo ga hanaseru hito ga kanarazushimo eigo ga tokui to wa kagiranai.
People who can speak a foreign language are not always good at English.
Benkyou jikan ga ooi seito ga kanarazushimo shiken de tensuu ga takai to wa kagiranai.
Students who study a lot are not necessarily scoring high on exams.
Practice
Grammar content sourced from hanabira.org.