Why does "seis" (six) have no accent, but "dieciséis" (sixteen) has? The stress appears to be in the same place in both words, doesn't it?

Question

Why has "seis" (six) no accent, but "dieciséis" (sixteen) has? The stress appears to be in the same place in both words, doesn't it (on the penultimate syllable)?

What a great observation. I never noticed! - Jeremias, Jan 8, 2012

Answer 1

Without the accent on "dieciséis", it would be pronounce as "diecíseis".

The accent is there to maintain the stress on "seis".

Just like with:

Veintiséis

Veintiún.

Veintidós.

Veintitrés.

Answer 2

Seis only has one syllable, so it doesn't need an accent mark. Dieciséis has 3 syllables and would be stressed on the next-to-last syllable if it didn't have an accent mark because it ends with an S.

Technically "dieciséis" has three syllables. - Naomi_Callas, Jan 8, 2012

Right your are. I haven't had my coffee, yet. :-) - KevinB, Jan 8, 2012

No problem, amigo. Good morning. :-) - Naomi_Callas, Jan 8, 2012

Answer 3

Actually, that's the last syllable. The combination of "e" and "i" is a dipthong. Therefore, "seis" is just one syllable, and does not need an acento ortográfico. "dieciséis" on the other hand, needs it because it is an oxytone word that ends in "s".

Answer 4

I really like the question, but with all the respect to all answers that have been give here I am not convinced of any of them. I think that it is something we have to accept it the way it is. I wonder if anyone can explain why such a word like matemáticas carry a tilde.

According to the answers that are given here words such as diecisiete should be written diecisiéte...

Un saludo afectuoso a todos

It's already clear how to pronounce diecisiete because when a word ends with a vowel, you stress the syllable that precedes it, so the accent isn't needed. When you pronounce dieciséis, on the other hand, rules of pronunciation tell you that you stress - GraceM, Jul 19, 2013

the syllable prior to the final syllable when a word ends with an s. Dieciséis is an exception, however, hence the need for the accent. So it's definitely needed, not just something you have to accept. :) - GraceM, Jul 19, 2013

Matemáticas absolutely needs the accent, otherwise you would have to pronounce it matemateeeecas, and that sure sounds funny. - Melita, Jul 20, 2013

Answer 5

Hi:

And also, it's to remind that seis is a complete word in itself (like uno, dos, tres in veintiún kilos, veintidós días, veintitrés páginas, dieciséis años).

Answer 6

Thanks for all your answers folks!

If you view 'seis' as a single syllable -- because it's a diphthong -- rather than two syllables (my first impression), then all becomes clear and logical. To me, at anyrate!