Stress in Spanish is marked unequivocally through a series of orthographic rules. The default stress is on the penultimate (next-to-last) syllable on words that end in a vowel, or and on the final syllable when the word ends in any consonant other than or . Words that do not follow the default stress have an acute accent over the stressed vowel. The written accent will thus appear only in certain forms of a word and not others, for example "andén", plural "andenes". In many cases, the accent is essential to understanding what a word means, for example "hablo" ('I speak') as opposed to "habló" ('he/she/Ud. spoke').