Transitive verbs may take a direct object.
Mi trinkas sukon. = I drink juice.
Mi sendas leteron. = I send a letter.
Intransitive verbs do not require a direct object.
Mi sidas. = I am sitting.
La akvo bolas. = The water boils.
In rare cases, some verbs can be transitive or intransitive, for example:
Mi drinkas. = I am drinking [alcohol to excess].
Mi drinkas bieron. = I am drinking beer [to excess].
Differences between Esperanto and English
Please note that the rules concerning verbs and objects are often more strict in Esperanto than in English.
In English, we know a lot of verbs that can be used both with and without a direct object. Take for example the verb "to close". It is usually used with an object: "I close the shop". But it is also possible to say "The shop closes", which we understand to be more or less equivalent of "The shop is being closed" or maybe "The shop closes itself".
In Esperanto, upon hearing "La butiko fermas -- (The shop closes --) we immediately ask ourselves: The shop closes what? And how can a shop even close something? It does not make sense. The verb fermi requires a direct object. (= "fermi" is transitive).
Let's look at another example: the transitive verb komenci (to begin, to start).
- correct: Mi komencas la laboron. (I begin the work.)
- also correct: Li komencas kuri. (He starts to run.)
- incorrect: La tago komencas --. (The day begins --.)
While in English it is fine to say "The day begins", in Esperanto we would immediately ask ourselves: The day begins what? - and this makes no sense. [Therefore, to express the idea of "The day begins" in Esperanto, we have to use the suffix -iĝ that we will encounter later in this course. "The day begins" = "La tago komenciĝas".]
How about sentences with transitive words that do seem perfectly fine even without an object? Although manĝi is transitive, as in Mi manĝas kukon (I eat/am eating cake), it is perfectly fine to say Mi manĝas (I eat/am eating) as we can easily imagine that I am eating, well, some kind of food. (We can, however, hardly imagine anything that a shop might be closing!)
Atendi can mean "to wait," "to wait for" or "to expect."
Mi atendas. = I wait.
Mi atendas buson. = I wait for a bus.
Mi atendas profiton. = I am expecting a profit.
Note: Kion vi atendas? can mean either "What are you expecting?" or "What are you waiting for?" depending on the context.