substance
The French word 'substance' is used in the same way as its English counterpart. It refers to a particular kind of matter with uniform properties. For example, water is a substance composed of hydrogen and oxygen atoms.
The substance of this speech is important.
This phrase is stating the importance of the essence or core content -- the 'substance' -- of a speech.
She discovered a strange substance in the dish.
In this sentence, the word 'substance' refers to some unidentified matter found in a dish.
The substance in the tube had a weird color.
This sentence is describing the color of a certain 'substance' found in a tube.