Learning Japanese Part 3

Part 2 of this series of my notes on learning Japanese introduced verbs and the formal and informal present tense inflections. I've also been learning the past tense.

Remember that all uninflected verbs end in a u:
書 to write Kaku (かく)
考 to think Kangaeru (かんげる)
来 to come Kuru (くる)

There are three "forms" of verbs.

1) Irregulars: of which there are only two: 来 and する (suru - to do)
2) All others ending in "ru": 考
3) All the rest: 書

Here's how to make the past participle of these verbs:
1) Formal: 来 becomes 来ました ("kimashita"); する becomes しました
1) Informal: 来 becomes 来た ("kita"); する becomes した ("shita")

2) Formal: -ru, +mashita: 考 becomes 考えました ("kangaemashita")
2) Informal: -ru, +ta: 考 becomes 考えた ("kangaeta")

3) Formal: -u, +imashita: 書 becomes 書きました ("kakimashita")
3) Informal: Now it gets trickier.

3i) if the verb ends in "ku", -ku, +ita (書 becomes 書いた - "kaita")

3ii) if the verb ends in "gu", -gu, +ida :
急 (いそぐ　"isogu", hurry) becomes 急いだ ("isoida")

3iii)if the verb ends in [nu|bu|mu], -[nu,bu,mu], +nda
学 (まなぶ 　”manabu"、learn) becomes 学んだ ("mananda")

3iv) if the verb ends in "su", -su, +shita
試 (ためす　”tamesu”, to experiment) becomes 試した（"tameshita")

3v) all other "u" and "tsu", -[u|tsu], +tta
立っ (たつ "tatsu", stand) becomes 立った ("tatta"). Note that the つ ("tsu")　character in the uninflected verb is not removed - it becomes the first "t" in った ("tta").

These forms are the same for all "persons" - that is, "I have written" is is "kaita" or "kakimashita". But "you have written" is also "kaita" or "kakimashita"