This is the 4877th most frequent Japanese word.
物質
"物質" means "matter" or "substance."
In this sentence, '物質' refers to 'matter' as a scientific concept encompassing all physical substances.
物質は固体、液体、または気体の形をとることができます。
Matter can exist in solid, liquid, or gas forms.
Here, '物質' refers to a 'substance,' implying a specific material with unknown properties.
何か未知の物質がこの部屋に存在しています。
An unknown substance exists in this room.
In this case, '物質' is used to mean 'matter' in a broad sense, relating to its general characteristics in scientific exploration.