La profesoro ridetis kaj diris, ke en februaro eĉ mallonga monato povas ŝajni longa, kiam oni tro multe laboras.

La means the. So La profesoro means the professor, referring to a specific professor, not just any professor.

Esperanto has only one definite article: la. It does not change for gender, number, or case.

Ridetis is the past tense of rideti, which means to smile lightly or to smile a little.

• ridi = to laugh
• rideti = to smile / to give a small laugh

The ending -is marks the past tense, so ridetis means smiled.

Kaj means and. It simply links the two past actions:

• La profesoro ridetis
• kaj diris

So the sentence says that the professor smiled and said.

Ke means that and introduces a subordinate clause.

After verbs like diri (to say), pensi (to think), scii (to know), and similar verbs, Esperanto often uses ke just like English uses that:

• Li diris, ke... = He said that...

Here, ke introduces what the professor said.

En februaro means in February or during February.

The preposition en is commonly used with months, seasons, and similar time expressions:

• en januaro = in January
• en somero = in summer

So en februaro is the normal way to say in February.

Mallonga means short.

It is built from:

• longa = long
• mal- = the opposite

So:

• longa = long
• mallonga = short

This is a very common Esperanto pattern. The prefix mal- often creates the opposite meaning of a word.

Eĉ means even.

It adds emphasis and shows surprise or contrast. Here it means that February is already a short month, but even a short month can feel long under certain conditions.

So eĉ highlights the unexpected part of the statement.

This is a common Esperanto structure:

• povas = can
• ŝajni = to seem
• longa = long

So povas ŝajni longa means can seem long.

With modal verbs like povi (can), Esperanto uses:

• a conjugated modal verb
• plus an infinitive

So:

• povas ŝajni = can seem
• povas labori = can work
• povas veni = can come

Because longa is not a direct object here. It is a predicate adjective after ŝajni (to seem).

The subject is mallonga monato. That month seems long.

In Esperanto, adjectives used after verbs like esti (to be) or ŝajni (to seem) stay in the basic adjective form -a, not the accusative -an.

Compare:

• La monato estas longa. = The month is long.
• La monato ŝajnas longa. = The month seems long.

But with a direct object, you would use -n:

• Mi vidas longan monaton. would mean something like I see a long month.

Because the professor said something that is presented as a general truth or general observation.

Esperanto does not automatically shift all subordinate verbs into the past just because the main verb is past. Instead, it usually uses the tense that matches the meaning.

So:

• diris = he said
• povas ŝajni = can seem
• laboras = one works / people work

This is natural because the statement is still true in general, not just at one past moment.

Oni is an impersonal pronoun. It often means:

• one
• people
• you in a general sense
• someone in a broad, unspecified sense

So kiam oni tro multe laboras means something like:

• when one works too much
• when people work too much
• when you work too much (general you, not a specific person)

It is very useful in Esperanto for general statements.

Tro multe laboras means works too much.

Here:

• tro = too, excessively
• multe = much / a lot
• laboras = works

So tro multe laboras literally means works too much / works excessively much.

This is the normal Esperanto way to express the idea. Tre laboras would sound more like works very intensely or would simply be less natural for works a lot. Esperanto usually uses multe labori for to work a lot.

In Esperanto, subordinate clauses are commonly separated by commas.

So:

• diris, ke... marks the clause introduced by ke
• longa, kiam... marks the clause introduced by kiam

This punctuation helps show the structure clearly and is very normal in written Esperanto.