Ĉi-matene mi veturis per biciklo al la librovendejo, sed ĉe la unua semaforo mi devis halti apud la trotuaro.

Ĉi-matene means this morning.

The element ĉi adds the idea of this or the present one, and in time expressions Esperanto often joins it with a hyphen:

• ĉi-matene = this morning
• ĉi-vespere = this evening
• ĉi-jare = this year

So this is a fixed, natural-looking time expression, not two separate words functioning like ordinary adjective + noun.

Because -is is the Esperanto ending for the past tense.

So:

• veturas = rides / travels
• veturis = rode / traveled
• devas = must / has to
• devis = had to

A useful Esperanto rule is that tense endings do not change with the person:

• mi veturis = I traveled
• li veturis = he traveled
• ili veturis = they traveled

That makes verb conjugation much simpler than in English.

Yes, mi biciklis would also be possible.

Veturi means to travel, ride, or go by vehicle. In this sentence, mi veturis per biciklo means that the speaker traveled using a bicycle.

A few related verbs:

• iri = to go, to walk, to move in general
• veturi = to go by vehicle
• bicikli = to cycle

So these are all possible in different contexts, but they are not exactly identical:

• Mi iris al la librovendejo = I went to the bookstore
• Mi veturis per biciklo al la librovendejo = I went there by bicycle
• Mi biciklis al la librovendejo = I cycled to the bookstore

The version in the sentence is very explicit about the means of transport.

Because per means by means of, using, or via, while kun means with in the sense of accompanied by or together with.

So:

• per biciklo = by bicycle / using a bicycle
• kun biciklo = with a bicycle

Kun biciklo could mean you have a bicycle with you, but it does not naturally express transportation method as clearly.

Compare:

• Mi venis per trajno = I came by train
• Mi skribas per krajono = I write with a pencil
• Mi venis kun amiko = I came with a friend

Al means to and shows direction toward a destination.

So:

• al la librovendejo = to the bookstore

This is the normal way to express movement toward a place.

Compare:

• en la librovendejo = in the bookstore
• ĉe la librovendejo = at the bookstore / by the bookstore
• al la librovendejo = to the bookstore

So the sentence uses al because the speaker is going toward that place.

La is the Esperanto definite article, equivalent to English the.

It is used when the noun is understood as a specific, identifiable thing:

• la librovendejo = the bookstore
• la unua semaforo = the first traffic light
• la trotuaro = the sidewalk

A few useful points:

• Esperanto has only one definite article: la
• It does not change for gender, number, or case
• There is no indefinite article corresponding to English a/an

So:

• librovendejo = bookstore / a bookstore
• la librovendejo = the bookstore

In this sentence, the speaker has specific referents in mind, so la is natural.

Yes. In Esperanto, semaforo normally means traffic light.

That can surprise English speakers because it resembles semaphore, but in everyday Esperanto usage semaforo is the ordinary word for the road signal with red, yellow, and green lights.

So:

• ĉe la unua semaforo = at the first traffic light

It is a good example of a word that looks familiar but is used a bit differently from the most obvious English look-alike.

Unua means first. It is an ordinal number, formed by taking a number and adding -a.

Examples:

• unu = one
• unua = first
• du = two
• dua = second
• tri = three
• tria = third

Because unua is acting like an adjective and describing semaforo, it has the adjective ending -a.

So:

• la unua semaforo = the first traffic light

Because devis halti means had to stop, not simply stopped.

• haltis = stopped
• devis halti = had to stop

So the sentence is not only describing the action. It also expresses necessity or obligation.

This is a very common Esperanto pattern:

• devi + infinitive

Examples:

• Mi devas iri = I must go
• Ŝi devis atendi = She had to wait
• Ni devos reveni = We will have to return

So devis halti is exactly parallel to English had to stop.

After devi, Esperanto normally uses the infinitive form of the main verb.

That is the form ending in -i:

• halti = to stop
• iri = to go
• atendi = to wait

So:

• mi devis halti = I had to stop

This works much like English modal structures:

• I must go
• I had to stop

Esperanto does not say something equivalent to mi devis haltis. After devis, the next verb stays in the infinitive.

They are similar, but not identical.

• ĉe means at, by, or in the area of
• apud means beside, next to

So:

• ĉe la unua semaforo = at the first traffic light
• apud la trotuaro = beside the sidewalk

In other words, ĉe gives a more general location, while apud gives a more precise idea of being right next to something.

That is why both can appear in the same sentence:

• the stop happens at the traffic light
• the speaker stops beside the sidewalk