The topic is a key concept in understanding Japanese. Roughly speaking, the topic of a sentence is what the sentence is about. For example, in the following sentence, the topic is Hanako, and the rest of the sentence provides information about Hanako.
(a) 花子は学生です。
Hanako wa gakusei desu. (Hanako is a student.)
(Speaking of Hanako, Hanako is a student.)
Topics are presented using various topic-marking devices. Among those, wa is the most frequent marker. When a topic is presented, it must be something both the speaker and the listener can identify from their knowledge. Typically, a topic is something mentioned in a previous discourse, something the speaker and listener perceive through their five senses, a proper noun, or a generic noun.
The direct object (sometimes referred to as just "object") of a verb is the direct recipient of an action represented by the verb. It can be animate or inanimate. An animate direct object is the direct experiencer of some action, while an inanimate direct object is typically something created, exchanged, or worked on — essentially, the recipient of the action of the verb.
The subject of a sentence indicates an agent of an action in active sentences (as shown in (a)), an experiencer of an action (as in (b)), or someone or something in a state or situation (as in (c), (d), and (e)). The subject is typically marked by the particle ga in Japanese unless it is the sentence topic.
(a) ジョンがりんごを食べた。
Jon ga ringo o tabeta. (John ate an apple)
(b) メアリーが先生にほめられた。
Mearii ga sensei ni homerareta. (Mary was praised by her teacher.)
(c)ナンシーはきれいだ。
Nanshii wa kireida. (Nancy is pretty.)
(d) ドアが開いた。
Doa ga aita. (The door opened.)
(e) 机が一つある。
Tsukue ga hitotsu aru. (Lit. One table exists. (=There is a table.))
An intransitive verb is a verb that does not require a direct object. The action or state identified by the intransitive verb relates only to the subject of the sentence. For example, the verb hashitta ("ran") in (a) is intransitive because the action of running pertains only to the subject.
(a) 山田さんは走った。
Yamada-san wa hashitta. (Mr. Yamada ran.)
Intransitive verbs typically indicates movement (such as いく 'go,' くる 'come,' 'あるく 'walk,'), spontaneous change (such as なる 'become,' かわる 'change,' とける 'melt'), human emotion (such as よろこぶ 'rejoice,' かなしむ 'feel sad,') and birth/death (such as うまれる 'be born," しぬ 'die).
A verb that requires a direct object. It usually expresses an action that acts upon someone or something indicated by the direct object. Actions indicated by transitive verbs include real causatives (such as いかせる 'make/let someone go,' ころす 'kill,' みせる 'show'), exchange (such as あげる 'give,' もらう 'receive,' communication (such as はなす 'speak,' かく 'write' かんがえる 'think'), and others. Note that some English transitive verbs are intransitive in Japanese.
A stative verb represents a state of something or someone at a certain point in time, as shown in (a).
(a) ある ari (exist (of inanimate things))
A punctual verb represents a momentary action that occurs once, as in (a), or can be repeated continuously, as in (b).
(a) しる shiru (get to know)
(b) おとす otosu (drop)
When combined with the auxiliary verb iru, the punctual verbs in (a) express a state after an action is completed, and those in (b) indicate either a repeated action or a state after an action is taken.