Here are the basic words/expressions that everyone needs to know. Once they have been mastered, you can focus on the other categories.
Basic Numbers/days
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Grammar Point: Present Tense
The present tense of a verb is formed by dropping the -ar (or -er or -ir) of the infinitive and using the appropriate ending. For example:
falar ("to speak") > eu falo ("I speak"); ele/ela fala ("he/she works").
Endings for regular -ar, -er and -ir verbs are as follows:
-ar (like falar): -o, -as, -a, -amos, -ais, -am
-er (like beber): -o, -es, -e, -emos, -eis, -em
-ir (like abrir): -o, -es, -e, -imos, -is, -em
Irregular verbs are less predictable. Here are some common ones for the "I" form:
dar ("to give), dou ("I give) /do/
fazer ("to do"), faço "I do") /fasu/
ver ("to see"), vejo ("I see") /vɐj.ʒu /
dizer ("to say"), digo ("I say") /digu/
ter ("to have"), tenho ("I have") /tɐ.ɲu/
You can find out more about the present tense of verbs here.