Will I learn words just by reading or hearing them?

If you read or hear a word a sufficient number of times, in a clear context that allows you to understand its meaning, you may ‘pick up’ that word and feel you have learnt it. However, generally the words we just see or hear but do not study and use remain in our ‘passive vocabulary’ – that is the vocabulary we understand but are not able use effectively. You need an active command of the vocabulary on the academic word list so that you can use it in your university work. This almost certainly means you need to study these words and practise them. However, reading and hearing these words frequently will certainly reinforce their meaning for you. However, you need to make sure you are reading the right texts – if you are reading fiction, you will meet many high frequency words but very few academic words.

See: What is the best way to learn new words? and What does it mean to learn a word?