Estoy seguro de que el libro verde es útil.

to be

Breakdown of Estoy seguro de que el libro verde es útil.

• el libro: the book
• yo: I
• estar: to be
• verde: green
• de que: that
• seguro: sure
• útil: useful

Questions & Answers about Estoy seguro de que el libro verde es útil.

Why do we say Estoy seguro and not Soy seguro?

In Spanish, estar is generally used for states or conditions that can change, whereas ser is used for inherent characteristics or permanent traits. Saying estoy seguro emphasizes a state of certainty (how I feel at this moment). Using soy seguro would sound odd, as it would imply being a sure (or secure) type of person by nature, which is not typically how Spanish speakers express confidence in a statement.

Why do we include de before que in Estoy seguro de que el libro verde es útil?

Certain Spanish verbs and expressions, such as estar seguro or darse cuenta, require a linking preposition (de) before que when introducing a subordinate clause. So, estoy seguro de que ... is the standard structure. Omitting de is more colloquial and, while you may hear it, estoy seguro que ... is less formal.

Could the sentence be Estoy seguro de que el libro verde está útil?

Typically, we use ser (es útil) with the adjective útil to describe its inherent function or quality: the book is useful by nature. Using estar útil is not common and would suggest a temporary condition (e.g., the book is in a useful condition right now, but that’s unusual phrasing in Spanish).

If I’m a female speaker, do I change the word seguro?

Yes. In Spanish, adjectives that refer to the speaker typically agree in gender. If you’re female, you would say estoy segura. Everything else in the sentence remains the same.

Does the placement of verde (after libro) change the meaning?

In Spanish, adjectives usually come after nouns, so el libro verde is the standard way to say the green book. In some cases, adjectives can precede the noun for emphasis or stylistic reasons, but the meaning here remains that the book is green.