Every word has a syllable that sounds with more emphasis: the stressed syllable. In casa the emphasis falls on ca; in camión, on ón. To find it, pronounce the word aloud and listen where the voice beat concentrates. That syllable serves to decide whether the word carries a written tilde. The accentuation is based on actual pronunciation, not on spelling. If you need to fine-tune how the syllables sound in Spanish, the review of Sounds and Phonetics helps to hear clearly the difference between weak syllables and strong syllables.

The tonic syllable in everyday words

Word	Notation	Description	Example
casa	ˈka.sa	The tonic syllable is the one that is pronounced with more strength in the word.	En casa descansan los gatos más elegantes.In casa the most elegant cats rest.
camión	kaˈmjon	The tonic syllable marks the strongest part of the word.	El camión lleva plátanos y una sombrilla.The camión carries bananas and a parasol.
murciélago	mur.ˈθje.la.ɣo	The tonic syllable can appear in a very long part of the word.	El murciélago ensayó un vals en la cueva.The murciélago practiced a waltz in the cave.

Acute-stressed words carry the emphasis on the last syllable. Café, reloj and avión are agudas because the final beat falls at the end of the word. They are written with an accent when they end in a vowel, in n or in s: canción, jamón, compás. If they end in another consonant, they do not carry an accent: pared, reloj, doctor. The key is to combine two data: last stressed syllable + ending in vowel, n or s. In quick reading, it is convenient to first focus on the final sound and then on the final letter.

When acute-stressed words carry an accent mark

Idea
Acute-stressed words carry an accent mark when they end in a vowel.
Acute-stressed words carry an accent mark when they end in n.
Acute-stressed words carry an accent mark when they end in s.

Llanas words have the emphasis on the penultimate syllable. Casa, árbol and joven belong to this group. They carry a tilde when they do not end in a vowel, in n or in s: árbol, fácil, lápiz. They do not carry it when they end in a vowel, n or s: mesa, joven, martes. In words that look very similar, the position of the stress changes the written meaning: camino is llana, while caminó is acute-stressed. When reading aloud, it is helpful to mark the penultimate syllable with more energy and check the ending.

When grave-stressed words carry an accent mark

Idea
Grave-stressed words carry an accent mark when they do not end in a vowel.
Grave-stressed words carry an accent mark when they do not end in n.
Grave-stressed words carry an accent mark when they do not end in s.

Esdrújula words have the stress on the antepenultimate syllable. Pájaro, teléfono and música are clear examples. All of them carry a written tilde, without exception. In pronunciation, the stressed syllable appears earlier than the ear usually expects: pá ja ro, te lé fo no, mú si ca. These words tend to have a very marked rhythm, useful for training listening and for practicing the pattern strong syllable + weak syllables, something that also appears in Rhythm and Meter.

Mandatory accent mark in proparoxytone words

Idea
Proparoxytone words always carry an accent mark.
Proparoxytone words always carry an accent mark even when they end in a vowel.
Proparoxytone words always carry an accent mark even when they seem very long.

Sobresdrújula words carry the stress before the antepenultimate syllable. They frequently appear in verb forms attached to pronouns: dímelo, explícaselo, cómetelo. All of them carry a written tilde. The stressed syllable falls very early in the word, and then several unstressed syllables follow. When pronouncing them, one feels a strong start and then a gentler fall. This group is often seen in commands and in combinations like verb + unstressed pronouns.

Mandatory accent mark in superproparoxytone words

Idea
Superproparoxytone words always carry an accent mark.
Superproparoxytone words always carry an accent mark when they join with pronouns.
Superproparoxytone words always carry an accent mark in long verb forms.

Most monosyllabic words do not carry an accent: sol, fe, mar, pan. Since they have only one syllable, there is no need to mark a stressed syllable ahead of another within the word. Pronunciation still rules: if one form is pronounced the same as another, the accent only appears when it helps distinguish meanings or grammatical functions. In normal writing, it is best not to add an accent by habit. The correct form arises from the actual syllable that is heard, not from an automatic rule about short words.

General use of accent marks in monosyllables

Idea
Most monosyllables do not carry an accent mark.
Pronunciation alone is not enough to put an accent mark on a monosyllable.
Only some monosyllables carry an accent mark to contrast meaning.

The diacritic tilde separates words that are spelled the same but do not mean the same thing. tu is possessive: tu casa; tú is a pronoun: tú sabes. el is an article: el libro; él is a pronoun: él llega. si introduces a condition: si vienes; sí affirms or functions as a pronoun: sí, claro; piensa en sí mismo. mas means but; más indicates quantity: quiero más. These pairs are recognized by the function they fulfill in the sentence, not only by how they sound. When the word has a diacritic tilde, the writing clarifies the exact meaning.

túelsímásmimastuélmísi

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Se usa para hablar directamente con otra personaSignifica lo mismo que pero en un estilo más literarioIndica cantidad mayor o comparaciónSignifica que algo pertenece a otra personaEs un artículo que acompaña a un sustantivoSirve para afirmar o para decir que algo ocurreSignifica que algo pertenece a quien hablaSe usa para referirse a una persona masculinaSe usa detrás de una preposición para referirse a quien hablaPuede expresar condición o duda

Common pairs with a diacritical accent mark

Word	Definition
tu	Means that something belongs to another person.
tú	Used to speak directly to another person.
el	An article that accompanies a noun.
él	Used to refer to a male person.
si	Can express a condition or doubt.
sí	Used to affirm or to say that something happens.
mas	Means the same as but in a more literary style.
más	Indicates a greater quantity or comparison.
mi	Means that something belongs to the person speaking.
mí	Used after a preposition to refer to the person speaking.

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