39951
I am just starting to learn Japanese, and with close to no knowledge
whatsoever, other than about the spelling system, I have noticed so many words
seen to end with the patterns suggested in the title of this post.

Can someone, in as brief and concise an explanation as possible, explain to me
why this is? Are these declensions of done nouns, adjectives, or verbs, or
other grammatical constructs I am observing?

Thanks.
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2016-10-13T08:08:29.453
39950
2016-10-13T09:13:48.380
18183
question
suffixes plural-suffixes
kimasu, shimasu, imasu, and mashite, and deshita
It is the formal (or polite) way of conjugating verbs.

書く (kaku) write (dictionary form)

書きます (kakimasu) write  
書きました (kakimashita) wrote  
書きません (kakimasen) don't write  
書きませんでした (kakimasen deshita) didn't write

私は本を書きます。 (watashi wa hon o kakimasu)  
I write a book.

です (desu) is  
でした (deshita) was  
ではありません (dewa arimasen) is not  
ではありませんでした (dewa arimasen deshita) was not

これは本です。 (kore wa hon desu)  
This is a book.
CC BY-SA 3.0
2016-10-13T09:13:48.380
39951
2016-10-13T09:13:48.380
18157
39950
answer