In Modals^x, Articles^x, Colons^x

Hello, this is my first post here, I like to know these words kilometer centimeter Are those words noun if they are standing alone ? if it's, what kind of noun it's, proper noun or abstract noun or etc ? After that, I want to indentify the part of speech of the following sentence by using the...

Hello, this is my first post here, I like to know these words kilometer centimeter Are those words noun if they are standing alone ? if it's, what kind of noun it's, proper noun or abstract noun or etc ? After that, I want to indentify the part of speech of the following setence by using the...

Thanks. I believe where an indefinite article may be used, the use of 'one' is justifiable too. My use of colon is acceptable too. 'Possibly' emphasise the degree of the probability. I was particularly interested in the use of modals. Thank you once more.