An important element in understanding verbs is the concept of INFINITIVES. Infinitives are unconjugated forms of verbs, typically interpreted as the “to” form, for example, “to eat”, “to drink”, “to sleep”.) Infinitives have not been broken down into the various six persons yet and they are recognized easily, as each one ends in the letter R. Spanish has three types of infinitives, those that end in AR, ER, and IR. Always remember that if you have two verbs side by side, there is a good chance that the second one will stay in the infinitive form, for example, “He wants TO STUDY”.

Then the word “Sonreírse” is in fact an already conjugated form of the verb infinitive SONREIR (TO SMILE), perhaps that verb is not used in that form because it is grammatically wrong; the right word for that enunciation would be REIRSE which means laugh(ing), because SONREIRSE would means literally “smile to ourselves or laugh of ourselves”.

the six persons are: yo(i), tu(you), el, ella(he, she); nosotros(we), ustedes(your) and ellos,ellas(they). plus the impersonal it referring to things or animals.

All the infinitive verbs ending with IR when in present tense must to end with the letters:

“IO” for the1st person YO(I) (singular)

“IES” for the 2nd person TU(YOU) (singular)

“IE” or “E” for the 3rd person(s) EL,ELLA(HE,SHE) (singular)

“IMOS” for the 4th person NOSOTROS(WE) (plural)

“EN” or “IEN” for the 5th person USTEDES(YOUR) (plural)

“EN” or “IEN” for the 6th person ELLOS, ELLAS(THEY)(plural)

and “IE” or “E” for the impersonal IT(EL, LA, = singular)

or “EN” or “IEN” for the impersonal IT( LOS,LAS =plural) OF THINGS OR ANIMALS

This is done by replacing the letters from the verb in infinitive form (IR) with these letters mentioned above as defined for each case

example:DORMIR( TO SLEEP)

YO duermO

TU duermES

EL,ELA duermE

NOSOTROS dormIMOS

USTEDES duermEN

ELLOS,ELLAS duermEN

and the impersonal

ELgato(the male cat) or LA gata(the female cat) duermE

LOS gatos(male,plural) /LAS gatas(female, plural) duermEN

All the infinitive verbs ending with IR when in past tense must to end with the letters:

“I” for the1st person YO(I) (singular)

“ISTE” for the 2nd person TU(YOU) (singular)

“IO” for the 3rd person(s) EL,ELLA(HE,SHE) (singular)

“IMOS” for the 4th person NOSOTROS(WE) (plural)

“IERON” for the 5th person USTEDES(YOUR) (plural)

“IERON” for the 6th person ELLOS, ELLAS(THEY)(plural)

and “IO” for the impersonal IT(EL, LA, = singular)

or “IERON” for the impersonal IT( LOS,LAS =plural) OF THINGS OR ANIMALS

This is done by replacing the letters from the verb in infinitive form (IR) with these letters mentioned above as defined for each case

example:DORMIR( TO SLEEP)

YO duermI

TU duermISTE

EL,ELA duermIO

NOSOTROS dormIMOS

USTEDES duermIERON

ELLOS,ELLAS duermIERON

ELgato(the male cat) or LA gata(the female cat) duermIO

LOS gatos(male, plural) /LAS gatas(female, plural) duermIERON

Then the infinitive verb SONREIR in present tense would be in this way:

yo sonríO

tu sonríES

el sonríE, ella sonríE

nosotros sonreIMOS

ustedes sonríEN

ellos sonríEN, ellas sonríEN

The infinitive verb SONREIR in past tense would be in this way:

yo sonreÍ

tu sonreISTE

el sonrÍO, ella sonrÍO

nosotros sonreIMOS

ustedes sonrIERON

ellos sonrIERON, ellas sonrIERON

SIMPLE PRESENT(ACTIVE TENSE)

YO SONRIO MUCHO(i smile a lot)

TU SONRIES MUCHO(you smile a lot)

EL SONRIE MUCHO(he smiles a lot)……etc

SIMPLE PRESENT (PASSIVE TENSE)

LOS PROGAMAS DE TV SON MUY REIDOS(TV shows are lot laughted)

PRESENT PROGRESSIVE(ACTIVE TENSE)

ESTOY SONRIENDO MUCHO(I am smiling a lot)

ESTAS SONRIENDO MUCHO (you are smiling a lot)..etc

PRESENT PROGRESSIVE(PASSIVE TENSE)

ESTOY SONRIENDO POR ADELANTADO(I am smiling in advanced)

ESTAS SONRIENDO POR ADELANTADO(you are smiling in advanced)etc….

SIMPLE PAST(ACTIVE)

EL HOMBRE TRISTE SONRIÓ PR PRIMERA VEZ

(the sad man smiled first time)

PASIVE

NUNCA HABIA SONREIDO

(he smiled never before)

PRESENT PERFECT(ACTIVE)

ALGUIEN HA SONREIDO CON NOSOTROS

(someone has smiled to us)

(PASSIVE)

SIEMPRE HAN ESTADO SONRIENDONOS

(they has been always smiling to us)

PAST PERFECT(ACTIVE)

ELLOS SONRIERON CON NOSOTROS AYER

they did smiled us yesterday

PASSIVE

HABIAN ESTADO SONRIENTES TODO EL DIA

they had been smiled the whole day..

MODALS(ACTIVE)

PUEDES SONREIR

you can smile

(PASSIVE)

ESPERO HAYAS SONREIDO

(I hope you smiled)

and so on………

you have to forgive me if any misspelling in my writing

I hope this could help you.

This is the way we do it in mexico

Presente

Yo sonrío

Tu sonríes

El/ella sonríe

nosotros sonreímos

ustedes sonríen

ellos sonríen

pasado

yo sonreí

tu sonreíste

él/ella sonrió

nosotros sonreímos

ustedes sonrieron

ellos sonrieron

Present

yo sonrio

tu sonries

el/ella/Ud. sonrie

nosotros sonreimos

vosotros sonreis

ellos/ellas/Uds. sonrien

Past

yo sonrei

tu sonreiste

el/ella/Ud. sonrieron

nosotros sonreiamos

vosotros sonreisteis

ellos/ellas/Uds. sonrieron

past =sonrio (with an accent on the o)

present = sonreir