Your Modern Japanese Class didn't leave you sufficiently prepared for Classical. Let's fix that.
The real meat and potatoes of Classical Japanese is that conjugation table. What I want to do for you is bridge the back page of your modern Japanese conjugation tables with enough knowledge that you can jump tentatively from modern to classical rather than take a leap of faith and fall in a river.
The average learner's Japanese text book does NOT give you enough to work with to actually pivot to Classical with an adequate level of understanding of grammar.
Transcribing this PDF 日本語文法の基礎 page 10, from left to right...
All the words in the universe can be divided into about 10 groups:
付属語 dependent or bound or 自立語 independent words.
Among dependents, words are split based on whether they 1. 活用する conjugate 助動詞 bound auxiliaries 2. or not 助詞 post positional particles.
Independent words are also split based on whether they conjugate or not.
Non-conjugating words which cannot become modifiers are split based on function. 3. Non-modifiers which can stand on their own are 感動詞 exclamations 4. while words which connect things are called 接続詞 conjunctions.
Non-conjugating words which can become modifiers split based on whether they 5. modify inflected words 副詞 adverbs 6. or uninflected words 連体詞 adnominal adjectives. 7. Words which can serve as the subject 主語 of a sentence are 名詞 nouns.
Anything which conjugates can serve as a 述語 predicate.
8. 形容詞 Adjectives are straight forward enough. You know them as “い adjectives” or pure adjectives.
9. 形容動詞 nominal adjectives you may know them as “な adjectives”, but this is not the full extent of them.
10. 動詞 verbs are used to express actions, movements, or existence. The base form of a verb ends in an ウ sound.
Pure Adjectives 形動詞 and Nominal Adjectives 形容動詞
Adjectives all end in ~い but you may have noticed that there are a lot of adjectives that end in ~しい specifically, like 新しい. Stick a pin in that. It's an important distinction to note. In Classical, those are split into two separate conjugation tables.
Nominal Adjectives are weird because they fall into a category where they act like adjectives but appear to look like nouns. But then why does it back translate to “adjectival verb” you may ask. According to this article the reason they are considered part 動詞 is how you would conjugate one in a sentence. The Modern language smooths out some of the distinctions that exist in Classical. (Also according to the article, there are linguists who want to reclassify them as 形容名詞 “adjectival nouns” but this hasn't picked up yet.)
You'll have been introduced to nominal adjectives by them ending in な to describe other things. 元気な男の子. But have you ever tripped up on a と where you expected に in stead?
- 堂々と走り回る
- 暗澹（あんたん）たるところ
Jisho.org describes these as “たる” adjectives. They are a leftover from Classical as well. Modern Na and Taru adjectives are the modern forms of Classical Nari and Tari adjectives respectively. Classical likes to slur letters together when they come before the verb あり (the verb “to be” used to be irregular. It's regular now).
- Shizuka (base) + ni + ari => shizuka n+ari
- Antan (base) + to + ari => antan t+ari
Everything you weren't taught about verbs and need to know before you open a Classical grammar reference.
Linguistics talk you didn't need but I'm giving you anyways.
A synthetic language is a language that is statistically characterized by a higher morpheme-to-word ratio. (Wikipedia).
Among these are Agglutinating, Fusional, and Polysynthetic language types. Polysynthetic are languages (eg. Indigeonous languages of North America) that string together large volumes of morphemes into a single unit. You can have a whole sentence worth of thought in what amounts to a single word. A fusional language involves an array of inflected morphemes, but there is a limit to how many of those morphemes you can use at a time. Most members of the Indo-European family are fusional. English is an oddball for a lot of reasons. At this point you could call it partially fusional since the only inflected ending we care about is third person singular “-s” vs everything else. Spanish is a better example of a fusional language. Japanese is an agglutinative language. It can glue together more morphemes than a fusional language but not nearly as hard core as a polysynthetic. In contrast, the Chinese family are Isolating languages since their morpheme to word ratio is nearly 1:1, and nothing inflects.
Verbs
Modern Japanese has 5 types of verbs: 五段活用、上（かみ）一段活用、下（しも）一段活用、カ行変格活用、サ行変格活用
A Five Step 五段 verb is what you already know as an “U” Verb. “U” verbs have a form ending in one of every vowel in the Japanese language.
A One Step 一段 verbs are what you already know as “Ru” Verbs. “Ru” verbs do not change their vowel stem no matter what form they are in. The Upper 上 indicates a stem vowel is -i- while the Lower 下 indicates a stem vowel of -e-.
The irregular 変格 verbs are home of one variety each, くる and する.
Japanese verbs conjugate into 6 forms, in this order.
- 未然形 irrealis form
- 連用形 continuative form
- 終止形 terminal form
- 連体形 attributive form
- 仮定形 conditional form
- 命令形 imperative form
These words may sound scary but you know enough kanji to know what they mean by now.
The irrealis form is for 未だ not yet. Things that haven't been completed. The “imperfect”. To this form, you can attach 助動詞 bound auxiliaries representing the potential れる -reru, passive れる -reru, causative せる -seru, negative ない -nai or ぬ -nu, and volitional う –(o)u.
The continuative is used for connecting 連 things. This is the form used for stacking compound verbs, for desiderative -tai たい or -tagaru たがる, situational -sou da そうだ, gerund -te て and even the perfect aspect -ta た. The polite register -masu ます also goes here because it was a stand alone honorific verb long ago, but now it isn't.
The terminal is the end 終止 of a sentence. There are a few modifiers you can tack on top of that too, such as hearsay -sou da そうだ, presumption -rashii らしい and expectation -beki べき. The Terminal form also doubles as the 基本形 Basic form of a verb.
The attributive is for making relative clauses and assumptions you da ようだ. (The Terminal and Attributive forms look identical in Modern Japanese. I have seen some texts refer to a combination 終止・連体形 Terminal-Attributive Form but this doesn't seem to have caught on either. In Classical they are more distinct.)
The conditional is for hypotheticals 仮定. Classical replaces this with the 已然形 realis form, already happened 已(すでに). They look the same; they just take different particles.
The imperative 命令 is for direct commands.
A Verb 動詞 conjugates 活用 into a form 形, and that form is used to hook up to a bound auxiliary 助動詞. And each of those bound auxiliaries can additionally conjugate into longer and longer strings.
And you already have most of the conjugation patterns in your head! They just look scary when they're spelled out with big words.
れる conjugates the same way any verb with an -e stem does. ない conjugates like an い adjective. たがる conjugates like a 5 step verb. If you end a verb with “let's” ~よう, you can't tack anything else on it. And then some of them are just special cases. です is weird. It does its own thing.
Do not be afraid of fancy terminology. I swear this isn't scary at all.
Example short cut
Think of it like this...
買う【五段】 買わない・買おう 買いたい・買って 買う。 買うこと 買えば 買え！
起きる【上一段】 起きない・起きよう 置きたい・起きて 起きる。 起きること 起きれば 起きろ！起きよ！
集める【下一段】 集めない・集めよう 集めたい・集めて 集める。 集めること 集めれば 集めろ！集めよ！
来る【カ行変格】 こない・こよう きたい・きて くる くること くれば こい
する【サ行変格】 しない・せぬ・される したい・して する。 すること すれば しろ・せよ
Example sentence
使わせられなければ、入院されなかったろう。 Tsukawaserarenakereba, nyuuin sarenakattarou.
If [I] had not been made to use [it], perhaps [I] would not have been hospitalized.
The first verb has the 基本形 basic form 使う tsukau, “to use”. Because it ends in う u, we can assume it is a 五段 five step conjugation pattern. After the verb stem 語幹 is “wa” indicating the verb is in the 未然形 irrealis form. The bound auxiliary 助動詞 after that is -se–, indicating the causative. This too is in irrealis. Causative -seru conjugates like a Lower One Step verb. The bound auxiliary after that is -rare– and it is still in the irrealis form. Passive -reru also conjugates like a Lower One Step verb. After that is -nakere– which is the negative -nai in the hypothetical form 仮定形 followed by the 助詞 particle ば -ba indicating a conditional.
The second verb is a compound Noun “hospitalization” + する suru, “to do”. Suru is an irregular verb, so its verb stem is just s-. It is in the irrealis form to attach the passive -re- again. Passive -reru also conjugates like a Lower One Step verb to take the negative -nai in a compound form. -Nai conjugates like an adjective. It is in the connective form 連用形 because the next part is an allision of なく naku + the verb “to be” aru ある. -aru is also in the connective form to facilitate the perfect aspect particle ta た. -Ta uses the same allided conjugation pattern that gerund te て does, which is why the connective stem -i- disappears. -ta is in the terminal form 終止形 because the final auxiliary is also an allision of だろう darou. Darou is comprised of the conclusive particle だ da in the irrealis form ending in the conjectural -u う.
In summary:
Tsukaw-ase-rare-nakere-ba, nyuuin s-are-nak-a-tta-rou.
Not so scary anymore?