Yes, 'outside' and 'inside' are nouns that can be used prepositionally and adverbially. As nouns they follow rules for 'the' like any other noun, but as prepositions or adverbs, 'the' is not used. Examples: As nouns: 'I liked the outside of the cathedral' 'The inside of the box is made of wood' 'He took a picture from the outside (of the building), but he didn't go in' 'Always make sure to clean the dust from the inside of your computer before replacing components' As adverbs: 'He went outside' 'Look inside!' 'Bob heard an ominous noise outside' 'I opened the window and a bird suddenly flew inside' As prepositions: 'She stood outside my house for two hours' 'A little old man could be seen sitting inside the shop' ---- As for 'from outside/inside' or 'from the outside/inside', there is little difference in meaning. The only instance where you would not be able to use 'the' is when describing the general state of being 'outside' (outdoors, out in the world etc.) or 'inside' (indoors): 'My cat likes to bring me birds from outside' ('the outside' would not be acceptable) Using 'from outside' and 'from inside' as prepositional phrases to describe motion is also a case when 'the' cannot be used: 'Bring in the chairs from outside the house' 'Take a box from inside the room and put it out here' Hope that helps!

Hi, Jun! No, "the" is not needed in the first sentence: "I heard something outside". "move something from the outside to the inside": here "the" is used to show position. For example : "I can't bring my feelings from the inside (inside your being) out (for everyone to see)". Here "the" just shows position. I don't know if there are rules for how to use it. (except if you're referring to something specific: the fish, the cloud ect.)