Affirmatives
negatives
pensar (stem changer)
dormir(stem changer)
100

something

what is "algo"?

100

nothing

what is "nada"?

100

we think

what is "nosotros pensamos"?

100
I sleep

what is "duermo"?

200

someone

what is "alguien"?

200

no one

what is "nadie"?

200

I think

pienso

200

we sleep

what is "dormimos"?

300

some 

what is "algunos/as"?

300

none

what is "ningun/ninguno/a"?

300

you think

what is "tu piensas"?

300

you sleep

what is "duermes"?

400

always 

what is "siempre"?

400

never

what is "nunca"?

400

you(formal), he, she thinks

what is "piensa"?

400

they sleep

what is "duermen"?

500

also/too

what is "tambien"?

500

neither, nor

what is "ni ni"?

500

they think

what is "ellos piensan"?

500

you(formal), he, she, sleeps

what is "duerme"?