Verb forms and tenses

Hi there!


The 5 bases you are referring to I am assuming are the -masu endings.

Eg. およぎます oyogimasu I swim
　　およぎません oyogimasen I don't swim
　　およぎました oyogimashita I swam
　　およぎませんでした oyogimasendeshita I did not swim.
　　およぎましょう　oyogimashou Let us swim. (volitional)

You need to add the -masu -masen -mashita -masendeshita -mashou endings to the stem of the verb, which is obtained by dropping the -ru or by changing the last u--->i

eg. たべるーー＞たべーー＞たべます
　　もぬーー＞のみーー＞もにます

Some phonetic changes might be necessary eg. tsu-->chi

eg.　まつーー＞まちーー＞まちます

In response to your question about politeness, you have polite and plain forms of verbs.

For example,

りんごをたべる？　"Ringo o taberu?" would be said between friends, where "taberu" is informal. Also called the dictionary form.

おちゃをのみますか？　"Ocha o nomimasu ka?" would be said between people not too familiar with one another. It's the -MASU ending which you'll see a lot.

めしあがってください！　”Messhiagatte kudasai" which means "Please eat" is honorific,
It is composed of the -te form of "meshiagaru" the honorific version of "taberu" and the imperative of "kudasaru", the polite form of "kureru", to give.

The -ta form is the simple past tense, for example きのうは、ぎんこうにいった。
" Kinou wa, ginkou ni itta." Yesterday, I went to the bank" (plain).


However, the -masu ending are for polite speech. There are many other conjugations and endings for informal speech. A full list can be found here:

http://www.as.ua.edu/nihongo/verb(underscore)table(underscore)roomaji.htm

Replace (underscore) with "_". I can't seem to put underscores in web addresses when I post them.

ロケットジャパニーズで　べんきょ　たのしんで　ください！

Just looked up these bases.

I've never seen them before. I would probably say just learn the conjugations of the different tenses, as there aren't that many, and nearly all verbs are regular.

The Rocket Japanese Course deals with many of the tenses, but I cannot seem to find a lesson that deals with all the conjugations at once.

I would suggest just progressing through the course, as it does a good job of explaining the uses of the different conjugations. Pay attention in the audio lessons as well, as salient points regarding grammar and tense usage are made.