Concept:
International Mother Language Day is observed every year on 21st February to promote linguistic and cultural diversity. It commemorates the sacrifice of students who fought for the recognition of their mother tongue.
• The movement took place in 1952.
• It happened in East Pakistan (present-day Bangladesh).
• Students demanded recognition of Bengali as an official language.
Step 1: Understand the historical background.
In 1948, Urdu was declared the only official language of Pakistan. This decision was opposed by the Bengali-speaking population.
Bengali speakers demanded equal recognition for their language.
Step 2: Identify the language movement.
On 21st February 1952, students protested in Dhaka for:
Recognition of Bengali language
Many students lost their lives during this protest.
Step 3: Connect it with International Mother Language Day.
UNESCO declared:
\[
21^{st}\text{ February as International Mother Language Day in 1999}
\]
to honor those martyrs.
Step 4: Final conclusion.
Thus, the language associated with this movement is:
\[
\boxed{\text{Bengali}}
\]