How to Say "dangerous" in Spanish
The most common Spanish word for “dangerous” is “peligroso” — use 'peligroso' when referring to something that poses a direct threat or risk of harm.
peligroso
peh-lee-GRO-sopeliˈɡɾoso
Examples
Cuidado, el perro es peligroso.
Be careful, the dog is dangerous.
Conducir con nieve es muy peligroso.
Driving in the snow is very dangerous.
Es una situación peligrosa para la economía del país.
It's a dangerous situation for the country's economy.
Matching the Noun: `peligroso` vs. `peligrosa`
Like most Spanish describing words, peligroso changes to match the thing it describes. Use peligroso for masculine things (un camino peligroso) and peligrosa for feminine things (una idea peligrosa).
Using `ser` vs. `estar`
Mistake: “La calle está peligrosa.”
Correction: Use `ser` (es peligroso) for something that is *always* dangerous, part of its nature. Use `estar` (está peligroso) for a *temporary* danger. For example: 'El mar *es* peligroso' (The sea is generally dangerous) vs. 'El mar *está* peligroso hoy' (The sea is dangerous today because of a storm).
inseguro
een-seh-GOO-rohinseˈɣuɾo
Examples
Este barrio es un poco inseguro de noche.
This neighborhood is a bit unsafe at night.
Ese puente parece inseguro.
That bridge looks unstable/unsafe.
Invertir todo tu dinero en una sola empresa es muy inseguro.
Investing all your money in a single company is very risky/unsafe.
Describing Places
When talking about a neighborhood or city, we almost always use 'ser' (Este lugar es inseguro) because it is seen as a characteristic of that place.
Confusion with 'unsecure'
Mistake: “La puerta está unsecure.”
Correction: La puerta es insegura (or 'no es segura'). Spanish uses 'inseguro' for both emotional and physical safety, unlike English which has many specific words.
radiactivo
rah-dyahk-TEE-bohraˈðjak.ti.βo
Examples
El uranio es un elemento muy radiactivo.
Uranium is a very radioactive element.
Debemos tener cuidado con los residuos radiactivos.
We must be careful with radioactive waste.
La zona fue evacuada por una fuga radiactiva.
The area was evacuated due to a radioactive leak.
Matching the Noun
This word changes its ending to match what you are describing. Use 'radiactivo' for masculine words (el material) and 'radiactiva' for feminine words (la sustancia).
Word Placement
In Spanish, technical adjectives like this almost always come AFTER the noun they describe. Say 'material radiactivo', not 'radiactivo material'.
The 'O' vs 'A' spelling
Mistake: “Muchos estudiantes escriben 'radioactivo' con O.”
Correction: While 'radioactivo' is common and accepted, 'radiactivo' (with an A) is the version preferred by official Spanish language experts (RAE).
Pelígroso vs. Inseguro
Related Translations
Learn Spanish with Inklingo
Interactive stories, personalized learning, and more.