menor
meh-nohr

younger, youngest; fewer, smaller, smallest

1.  Soy la menor de mis hermanas.

I am the youngest of my sisters.

2.  El suéter que me regalaron mis padres para mi cumpleaños no me quedó; necesito una talla menor.

The sweater my parents got me for my birthday didn't fit; I need a smaller size.

How do you know if no 1 is I am the youngest of my sisters or I am the smallest of my sisters

I am the smallest of my sisters would be:

Soy la mas pequeña de mis hermanas