I believe its when its being used as an adjective and under 100.
we can use tough instead of hard.
Use a semi-colon instead
This word is not known in English, you should submit an explanation as to how it is used in a sentence
A fluent flipping sentence!!
No you shouldn't, unless it is at the start if a sentence.
This is a run-on sentence ( should be two sentences) with a spelling error.
Example sentence - I knew I should do my homework myself instead of cheating by using websites.
The correct spelling is environment.An example sentence is "the environment should be looked after".
Instead is an adverb, but it can act as a conjunctive adverb where it modifies a clause or previous sentence. (He should have fled. Instead, he tried to fight the fire.)
The word radious should never be used in a sentence since its spelling is incorrect and it is not possible to determine whether the intention was to write radius or radios.
Sentence-level Revisions
use "that" when the meaning of the sentence changes. Sometimes "that" can be left out of the sentence. Never use a comma with "that". Use "which" when the meaning of the sentence does not change. Always use a comma with "which".