Tio estas mia unua libro.

That is my first book.

Breakdown of Tio estas mia unua libro.

• esti: to be
• libro: the book
• mia: my
• tio: that
• unua: first

Questions & Answers about Tio estas mia unua libro.

What does tio mean here, and what kind of word is it?

Tio is a demonstrative pronoun.
In this sentence it means roughly “that (thing)” or simply “that” as the subject of the sentence.

So Tio estas mia unua libro. = That is my first book.

Grammatically, tio is:

• demonstrative: it points to something (usually something visible or just mentioned)
• pronoun: it stands on its own and is not directly attached to a noun

How is tio different from tiu or ĉi tio?

• tio = “that (thing)” in a general, neutral sense.

  • Example: Tio estas interesa. – That is interesting.

• tiu = “that one / that (person/thing)” and is normally used with a noun or when the noun is clearly understood.

  • With a noun: Tiu libro estas nova. – That book is new.
  • Without a noun (but understood): Mi volas tiun. – I want that one.

• ĉi tio = “this” (literally “this here thing”).

  • Example: Ĉi tio estas mia unua libro. – This is my first book.

In your sentence, Tio estas mia unua libro, tio is the subject and it points to some book that is being referred to, usually “that (one)” rather than “this (one)”.

Why is the verb estas the same for tio, mi, ili, etc.? Doesn’t it change like am / is / are?

In Esperanto, verbs do not change with the subject in the present tense.

• esti is the infinitive “to be”.
• The present tense form is estas for all subjects:
  • Mi estas – I am
  • Vi estas – you are
  • Li/ŝi/ĝi estas – he/she/it is
  • Ni estas – we are
  • Ili estas – they are
  • Tio estas – that is

So in Tio estas mia unua libro, estas is simply the present tense of esti, and it doesn’t change form because of tio.

Why isn’t there a word for “a” (as in “a book”) in the sentence?

Esperanto has only one article, la, which corresponds to English “the”.

There is no separate word for “a” or “an” in Esperanto. Indefiniteness is usually understood from context.

• Libro can mean “a book” or “book” in general.
• La libro would mean “the book” (a specific one).

So:

• Tio estas mia unua libro.
  = That is my first book. (no need for a separate “a”)
• If you really wanted to stress “one book (not two)”, you’d use unu, but that has a different role (see next question).

What is the difference between unu and unua, and why do we use unua here?

• unu is the cardinal number “one”.

  • Example: Mi havas unu libron. – I have one book.

• unua is the ordinal number “first”.

  • In Esperanto, ordinal numbers are formed by taking the number and adding -a:
    • unu → unua (one → first)
    • du → dua (two → second)
    • tri → tria (three → third), etc.

In mia unua libro:

• unua is an ordinal adjective meaning “first”.
• So mia unua libro = my first book (not “my one book”).

Why does unua end in -a? Is it an adjective?

Yes. In Esperanto, adjectives always end in -a.

• bona – good
• granda – big
• interesa – interesting
• unua – first

Even though unua comes from the number unu, it behaves like a normal adjective:

• unua libro – first book
• duaj libroj – second books
• tria ĉapitro – third chapter

So unua is an adjective describing the noun libro.

Why is it mia and not mi before unua libro?

Mi means “I” (the subject pronoun).
To make a possessive (my, your, his, etc.), Esperanto adds -a to the personal pronoun:

• mi → mia – my
• vi → via – your
• li → lia – his
• ŝi → ŝia – her
• ni → nia – our
• ili → ilia – their
• ĝi → ĝia – its

So:

• mi = I
• mia = my

In mia unua libro, mia is a possessive adjective meaning “my”, modifying libro.

Do adjectives in mia unua libro have to match libro in number and case?

Yes. In Esperanto, adjectives agree with their noun in:

• number (singular or plural: no ending vs -j)
• case (nominative vs accusative: no -n vs -n)

In your sentence, libro is:

• singular
• nominative (not a direct object)

So:

• mia unua libro

If it were plural, you would add -j:

• miaj unuaj libroj – my first books

If it were accusative (direct object), you’d add -n to all:

• Mi legis mian unuan libron. – I read my first book.
• Mi legis miajn unuajn librojn. – I read my first books.

Why doesn’t libro have an -n ending here?

The -n ending marks the accusative case, which is mainly used for direct objects and some expressions of direction.

In Tio estas mia unua libro:

• libro is not a direct object.
• It is part of the predicate after estas (a “predicate noun”), describing what the subject tio is.

In Esperanto, predicate nouns and adjectives after “esti” do not take -n:

• Li estas instruisto. – He is a teacher.
• Ŝi estas feliĉa. – She is happy.
• Tio estas mia unua libro. – That is my first book.

So no -n is needed on libro, mia, or unua in this sentence structure.

Can the word order be different, like Mia unua libro estas tio or Estas mia unua libro?

Esperanto word order is fairly flexible, especially in simple sentences like this.

All of these are grammatically correct, but differ in emphasis or style:

• Tio estas mia unua libro.
  Neutral, most usual: That is my first book.

• Mia unua libro estas tio.
  Closer to: My first book is that (one).
  Emphasis on which thing is your first book.

• Estas mia unua libro.
  Possible, but more like “It is my first book” in a general or contextual sense, where “it” (the subject) is understood from context. In careful teaching or formal style, people usually prefer to include an explicit subject like Tio or Ĉi tio.

Within the noun phrase mia unua libro, the normal, natural order is:

• [possessive] [adjective(s)] [noun]
  → mia unua libro

Something like unua mia libro or mia libro unua would sound strange or incorrect in normal Esperanto.

How would I say related sentences like “Those are my first books” or “That is my second book”?

Using the same patterns:

1. Those are my first books.

   • Tiuj estas miaj unuaj libroj.
     • tiuj – those (plural of tiu)
     • miaj – my (plural, agreeing with libroj)
     • unuaj – first (plural, agreeing with libroj)
     • libroj – books (plural of libro)

2. That is my second book.

   • Tio estas mia dua libro.
     • dua – second (ordinal of du)
   • Or if you want to say That book is my second book:
     • Tiu libro estas mia dua libro.

You can see the same structure as in Tio estas mia unua libro, just with different demonstratives (tio/tiu/tiuj) and ordinals (unua, dua).

Why not say Tiu estas mia unua libro instead of Tio estas mia unua libro?

You can say Tiu estas mia unua libro, but it has a slightly different feel:

• Tio estas mia unua libro.
  Focuses more on “that thing (there)” in a neutral way. It’s like pointing to an object and saying: “That is my first book.”

• Tiu estas mia unua libro.
  Feels more like “That one is my first book.”
  We often use tiu when:

  • contrasting one specific item with others:
    Ne tiu, sed tiu estas mia unua libro. – Not that one, but that one is my first book.
  • or when tiu clearly refers to a specific book/person among others.

Both are grammatically correct; tio is more neutral and common when you just point at something and identify it.

How do you pronounce Tio estas mia unua libro?

Esperanto pronunciation is very regular:

• Tio – TEE-oh

  • ti as in English tea
  • o as in lot

• estas – EH-stahs

  • e as in bed
  • a as in father
  • stress on the first syllable: ES-tas

• mia – MEE-ah

  • i as in machine
  • a as in father
  • stress on MI: MI-a

• unua – oo-NOO-ah

  • u as in food
  • stress on NU: u-NU-a

• libro – LEE-bro

  • i as in machine
  • o as in lot
  • stress on LI: LI-bro

Overall stress rule: always on the second-to-last syllable of each word.
So: TIO ES-tas MI-a u-NU-a LI-bro.