"Eu preciso de um segundo."

Translation: I need a second.

[NormanEdwa]

isn't "dum" a contraction for de+um , or "duma" for de+uma

[rabelo_ana]

It is a contraction, but only in speech.
You will probably hear someone say "Eu preciso dum segundo," but you will never see it written.

[PhilipCask]

That's why I couldn't understand the spoken version! Sounded like "doom" to me.

[MattBenet]

Could this be referring to both time or number? For example could you be asking someone to wait, but also, depending on the context, be asking for a second helping of dinner?

[ZuMako8_Momo]

No. This always means that one needs more time and that the other person needs to wait a bit. For another helping, you would probably ask if you could serve yourself again, a question to which any Portuguese person would reply something along the lines of, "Of course! Eat! Eat!" XD

[ChrisGull]

Does anybody else hear SEgundo instead of seGUNdo? Should it not be the latter, according to the rules when there are no acutes or circumflexes?

[Paulenrique]

yes, the emphasis must be on seGUNdo.

[Maureen624957]

Please explain the difference between um segundo and uma segunda; where they both mean 1 second.
Obrigada

[ZuMako8_Momo]

When you are looking for the word for the unit of time measurement equivalent to 1/60th of a minute, it is always «um segundo».

The words «segundo» and «segunda» are adjectives that mean "second." You can also turn them into nouns; for example, a woman who says, "I am the second one in line," would be «Sou a segunda na fila.».

Also, «segunda» can be short for «segunda-feira» = "Monday."

[o_scott]

Can the second be a person to back me up in a duel?

[Paulenrique]

Yes. It depends on the context.