Introduction
Learning when to use Alguém versus Algum is a common challenge for English-speaking learners of Brazilian Portuguese. Both words come from the same root but serve different grammatical roles: one refers to people and the other to things, and they follow different rules for gender, number, and agreement. This article explains the differences step by step with clear examples and usage notes.
Overview: People vs Things
Alguém is an indefinido that refers specifically to an unspecified person. It is singular and does not change for gender. Use Alguém when you mean somebody, someone, or anybody.
Algum is an adjective or pronoun that refers to an unspecified thing, quantity, or person in some contexts, and it must agree in gender and number with the noun it modifies. Use Algum when you mean some, any, or a certain amount/number of something.
Quick comparison
Alguém: pessoa indeterminada, sempre singular, não varia por gênero. Example: Alguém ligou.
Algum: acompanha substantivos, varia por gênero e número: algum, alguma, alguns, algumas. Example: Algum livro ficou na mesa.
Detailed grammar: Alguém
Alguém functions as an indefinite personal pronoun. It replaces a noun that denotes a person when that person is unknown, irrelevant, or not specified.
Form and agreement
Alguém is always singular and has only one form. It never changes to agree with gender or number. When referring to a known person whose gender matters, Portuguese speakers might add clarifying context, but the word itself remains the same.
Examples with translations
Alguém está na porta.
Someone is at the door.
Alguém me chamou ontem.
Somebody called me yesterday.
Alguém sabe falar inglês aqui?
Does anyone here know how to speak English?
Using alguém with verbs and pronouns
Because alguém is grammatically singular, verbs and pronouns must agree in the singular. Use third-person singular verb forms and singular pronouns when referring back to alguém.
Alguém trouxe o livro, e ele deixou em cima da mesa.
Someone brought the book, and he/they left it on the table. (Note: grammatical agreement uses ele but real gender may differ.)
Negative and question contexts
Alguém often appears in questions and negative contexts combined with negative words like ninguém and ninguém is used for nobody. In positive questions, use alguém; in negative statements, use ninguém.
Você viu alguém?
Did you see anyone?
Não vi ninguém na festa.
I didn’t see anyone at the party.
Detailed grammar: Algum
Algum is an indefinite adjective or pronoun that agrees with the noun it modifies in gender and number. It can mean some, any, or certain, and it is used for things, quantities, and also for people when directly modifying a noun.
Forms and agreement
There are four forms: algum (masculine singular), alguma (feminine singular), alguns (masculine plural), and algumas (feminine plural). Choose the form that matches the noun.
Examples modifying things
Algum dinheiro ficou na mesa.
Some money stayed on the table.
Alguma comida está estragada.
Some food is spoiled.
Preciso de alguns minutos.
I need a few minutes.
Examples modifying people
Algum aluno não entregou o trabalho.
Some student did not submit the assignment.
Algumas pessoas chegaram cedo.
Some people arrived early.
Using algum as a pronoun
Algum can act as a pronoun replacing a noun phrase. In that case, it still agrees in gender and number with the implied noun. When the noun is omitted, context determines the form.
Você trouxe frutas? Sim, trouxe algumas.
Did you bring fruit? Yes, I brought some.
How to choose: Alguém or Algum?
Decide based on whether you are talking about people or things, and whether the word must agree with a noun.
If the referent is an unspecified person and no noun follows, use Alguém. If you are modifying or replacing a noun (person or thing) and you need agreement in gender/number, use Algum or its form.
Decision flow
Is the referent a person and is no noun following? Use alguém.
Is the referent a noun (person or thing) that requires gender/number agreement? Use algum / alguma / alguns / algumas.
Examples side by side
Alguém me ajudou.
Someone helped me. (No noun follows; use alguém.)
Alguma pessoa me ajudou.
Some person helped me. (Noun pessoa follows; use alguma.)
Alguém trouxe flores.
Someone brought flowers.
Algumas pessoas trouxeram flores.
Some people brought flowers. (Agreement: algumas with pessoas.)
Negation and indefinite pronouns
Portuguese uses different indefinite words in negative and affirmative contexts. Understanding these helps choose correctly.
Alguém vs ninguém
Use alguém in positive contexts or questions expecting a possible yes. Use ninguém for nobody in negative statements. Remember that ninguém is singular and requires singular verbs.
Ninguém respondeu ao telefone.
Nobody answered the phone.
Algum vs nenhum
When using algum in affirmative statements, the negative counterpart is nenhum/nenhuma/nenhuns/nenhumas depending on gender and number. In negative contexts, prefer the negative form rather than combining não with algum, though spoken Portuguese sometimes uses não algum colloquially.
Tenho algum dinheiro.
I have some money.
Não tenho nenhum dinheiro.
I don’t have any money.
Common mistakes and how to avoid them
Mistake 1: Using algum when referring to an unspecified person without a noun. Correct to use alguém.
Wrong: Algum ligou para você.
Right: Alguém ligou para você.
Mistake 2: Forgetting agreement. Always match algum with the noun gender/number.
Wrong: Algum meninas chegaram.
Right: Algumas meninas chegaram.
Mistake 3: Using ninguém in a question where you expect a possible person. Use alguém instead.
Wrong: Ninguém sabe onde ele está?
Right: Alguém sabe onde ele está?
Stylistic and cultural notes
In Brazilian Portuguese, native speakers often choose simpler forms in spoken language. For example, questions with alguém may sound more natural than constructions using algum plus pessoa. Also, in informal speech you may hear contractions or dropped words, but written and formal Portuguese follows the rules above.
Brazilian Portuguese tends to use inclusive and neutral language patterns in many contexts, but traditional grammar keeps alguém as invariant and algum as variable. When referring to people, if gender is unknown and you must use an adjective form, choose the masculine plural if the group is mixed, or use nouns like pessoas to avoid gender issues.
Politeness and register
Using alguém in questions is neutral and polite. Using algum with pessoas can sound a bit distant or formal, depending on the construction. For everyday speech, Brazilians prefer straightforward phrases: Alguém pode me ajudar? instead of Alguma pessoa pode me ajudar?
Extra patterns and advanced uses
Indefinite pronouns combine with prepositions and other words to form expressions. For example, ninguém + preposition becomes ninguém com, ninguém de, etc. Similarly, algum can appear in quantified expressions or set phrases.
Alguém de confiança pode vir?
Can someone trustworthy come?
Algum tempo depois, ele voltou.
Some time later, he returned.
Negation with verb placement
When negating with ninguém or nenhum, the negative word typically precedes the verb. With alguém and algum, place the word where it most naturally modifies the noun or verb.
Ninguém apareceu.
Nobody showed up.
Eu não vi ninguém no parque.
I did not see anyone in the park.
Useful summary table (quick reference)
Use this short decision guide when in doubt:
If you mean somebody and no noun follows: alguém.
If you are modifying or replacing a noun and need agreement: algum / alguma / alguns / algumas.
Negative: use ninguém for people and nenhum/nenhuma for things, matching gender/number as needed.
Conclusion
Mastering the difference between Alguém and Algum helps you speak and write Brazilian Portuguese more accurately. Remember: alguém refers specifically to an unspecified person and never changes form, while algum and its variants agree with the noun in gender and number and can refer to people or things when modifying a noun. Pay attention to negation and agreement, and you will quickly become comfortable using both in everyday situations.
