Learn Hardcore Esperanto: La patrino respondas, ke ŝia tago estis pli maltrankvila ol lia, sed nun ŝi sentas sin trankvila. - The mother answers that her day was more anxious than his, but now she feels calm.

La patrino respondas, ke … = The mother answers that …
Everything after ke is the content of what she says: ke ŝia tago estis pli maltrankvila ol lia.

So ke works exactly like that in English sentences such as “She says that her day was …”.

Why is there a comma before ke: “respondas, ke …”?

In Esperanto it is normal (and stylistically preferred) to put a comma before ke when it introduces a subordinate clause.

So:

Ŝi respondas, ke…
Li pensas, ke…
Mi kredas, ke…

This comma marks the boundary between the main clause (La patrino respondas) and the subordinate clause (ke ŝia tago estis…). It isn’t strictly “grammar-required” in the way some languages require commas, but it is standard good style and very common.

Why is it ŝia tago and not sia tago?

Esperanto distinguishes between ŝia (“her”) and sia (“her own / his own / their own”, reflexive).

ŝia refers to some female person already mentioned, but not necessarily the subject of the same clause.
sia always refers back to the subject of that clause.

In this sentence:

Subject of the clause is ŝia tago (“her day”): the day is the subject, not the mother.
The possessor is “the mother” from the previous clause (La patrino).

Because the subject of estis is tago, and the owner of the day is la patrino (from the previous clause), we use ŝia, not sia.
Sia would only be used if the subject of estis were the same person who owns the day within that clause.

Who does lia (“than his”) refer to in “pli maltrankvila ol lia”?

Lia means “his”, referring to some male person mentioned earlier in the broader context (for example, her son, her husband, etc.).

In “pli maltrankvila ol lia”:

The full idea is “more restless than his (day)”.
The word tago is omitted after lia because it’s already clear from ŝia tago (“her day”).
Esperanto often drops repeated nouns:
- ŝia tago estis pli maltrankvila ol lia (tago).

So lia refers back to that earlier male person, whose day is being compared to hers.

Why is it tago and not tagon? Shouldn’t there be an -n somewhere?

No -n is needed because tago is the subject, not a direct object.

ŝia tago estis pli maltrankvila…
- tago is the subject of estis (“was”).
- Subjects in Esperanto stay in the basic -o or -a form, without -n.

You only add -n (accusative) when the word is a direct object or when marking direction (movement to somewhere). Here, nothing is being “acted on” by a verb like “have, see, read, eat”, so no accusative is needed.

How does the comparison “pli maltrankvila ol lia” work?

Esperanto uses:

pli … ol … = more … than …
malpli … ol … = less … than …

So:

pli maltrankvila ol lia (tago)
= more restless than his (day)

Structure:

pli + adjective + ol + thing being compared

Examples:

Ŝi estas pli alta ol li. – She is taller than him.
La filmo estis pli interesa ol la libro. – The film was more interesting than the book.

What does maltrankvila literally mean, and how does the prefix mal- work?

Esperanto uses mal- to form the opposite of a word.

trankvila = calm
maltrankvila = not calm → restless, worried, uneasy

So:

alta / malalta = tall / short
bona / malbona = good / bad
amiko / malamiko = friend / enemy

Here, maltrankvila is simply “the opposite of trankvila”.

Why is it estis in the first part and sentas (present) in the second part?

The sentence talks about two different time frames:

ŝia tago estis pli maltrankvila
- estis = was (past)
- Her day, which is already mostly over, was more restless than his.
sed nun ŝi sentas sin trankvila
- nune ŝi sentas = but now she feels (present)
- At the current moment she now feels calm.

So the past tense estis describes how the day went, and the present tense sentas describes how she feels right now.

Why do we say “ŝi sentas sin trankvila” and not just “ŝi sentas trankvila” or “ŝi sentas sin trankvile”?

In Esperanto, senti (“to feel”) usually takes:

a reflexive object: sin (“oneself”), and
an adjective describing the person.

So:

ŝi sentas sin trankvila
= literally “she feels herself calm”
= “she feels calm.”

Details:

sin is the reflexive pronoun = “herself”.
trankvila is an adjective describing ŝi (the subject), not sin as an object.

Why not ŝi sentas trankvila?
Because without sin, senti usually means “to perceive (with the senses)”:

Ŝi sentas la pluvon. – She feels the rain.

Why not trankvile (adverb)?
Trankvile would describe how she feels (in a calm way), not what she feels like.
To say what state she is in, Esperanto normally uses an adjective: trankvila.

So ŝi sentas sin trankvila is the standard way to say “she feels calm.”

Why is trankvila not trankvilan at the end of “ŝi sentas sin trankvila”?

Trankvila is an adjective that agrees with the subject (ŝi), not with sin.

The pattern is:

ŝi sentas sin trankvila
= “she feels herself [to be] calm.”

Grammatically:

ŝi = subject
sentas = verb
sin = direct object (accusative already inside the word sin)
trankvila = predicate adjective describing ŝi

Predicate adjectives in Esperanto do not take -n, because they’re not direct objects; they describe the subject (or sometimes another noun) via esti, resti, fariĝi, senti (sin), etc.

Compare:

Ŝi estas trankvila. – She is calm. (no -n)
Mi trovas lin amuza. – I find him amusing. (no -n on amuza)

So trankvila is correct; trankvilan would be wrong here.

Could the word order be different, for example “Sed ŝi nun sentas sin trankvila”?

Yes. Esperanto word order is quite flexible. All of the following are grammatically correct and natural:

Sed nun ŝi sentas sin trankvila.
Sed ŝi nun sentas sin trankvila.
Sed ŝi sentas sin nun trankvila.

The main rules are:

The verb can come fairly freely (often after the subject, but not always).
Adverbs like nun can move around to change emphasis, but they don’t change basic meaning.

The original choice “sed nun ŝi sentas sin trankvila” just slightly emphasizes the “now” contrast: before, the day was restless; now, she feels calm.