Mother Language refers to the first language of a person. Usually the people from Pakistan, the mother language is the Urdu. If you think about the people from Spain, their language is Spanish. People from USA, UK, the language is English.
We can have a brief of the history of this day from the Wikipedia mentioned below.
On 21 March 1948, Mohammed Ali Jinnah, the Governor general of Pakistan, declared that Urdu would be the only official language for both West and East Pakistan. The people of East Pakistan (now Bangladesh), having mother language Bangla, started to protest against this. On 21 February 1952, (8th Falgun 1358 in the Bangla calendar), students in the present day capital city of Dhaka called for a provincial strike. The government invoked a limited curfew to prevent this and the protests were tamed down so as to not break the curfew. The Pakistani police fired on the students despite these peaceful protests and a number of students were killed. Four of them were Abdus Salam, Rafiq Uddin Ahmed, Abul Barkat and Abdul Jabbar (Copied from the Wikipedia)
Bangla is the International Mother Language. I deeply remember those who sacrificed them for this achievement.
