Count to ten

uno one
dos two
tres three
cuatro four
cinco five
seis six
siete seven
ocho eight
nueve nine
diez ten
cero zero
veinte twenty
treinta thirty
cuarenta forty
cincuenta fifty
sesenta sixty
setenta seventy
ochenta eighty
noventa ninety
cien one hundred
contar to count

Mi hermanito tiene cinco años. My little brother is five years old.
Sólo fui a dos clases hoy. I only went to two classes today.
Ella compró nueve peces para su acuario nuevo. She bought nine fish for her new aquarium.
Seis de sus ocho primos viven en Brasil. Six of his/her eight cousins live in Brazil.
Hay siete días en una semana. There are seven days in a week.

Numbers
Numbers in Spanish are always in the singular form. Plural forms of numbers don't exist. Notice in the following examples that even though the noun is in a plural form, the number doesn't change. The number "one" has both a masculine and a feminine form "uno" and "una", but other numbers do not change for gender. For example:

cinco casas five houses
diez niños ten children
dos amigos two friends
una noche one night