Although many ignore or omit their use, tildes are fundamental in Spanish. Placing them correctly is essential to convey the right message. The Royal Spanish Academy (RAE) details the differences between the words 'si' and 'sí'.
'Sí' with a tilde has multiple uses. The most common is the affirmative: as a masculine noun for permission or agreement, and when preceded by a preposition (except 'con', which forms 'consigo'). The adverbial phrase 'de por sí' also takes a tilde, meaning 'by its very nature'.
On the other hand, 'si' without a tilde is an unstressed conjunction, usually conditional. It can express a real condition (possible fact) or a potential one (unlikely action), as in 'Si ganara el bingo, me compraría una casa'. It also appears in indirect interrogative clauses ('Me dijo que no sabía si saldría de vacaciones') and comparisons ('Se abriga como si estuviéramos en la nieve').
Additionally, the RAE explains the ethical dative, a grammatical resource exemplified in the sentence 'El nene no me come'. The pronoun 'me' indicates the person affectively involved in the action, expressing the mother's love and concern, without literal interpretation. The RAE's Glosario de términos gramaticales defines this usage as correct.
The section also addresses the lunula, the whitish semilunar space at the root of the nail, and petrichor, the scent of dry earth after the first rain. Words like 'cédula', 'aguja', and 'cápsula' come from Latin diminutives. The Dictionary of the Spanish Language lists nine meanings for 'cuarentena', including sanitary isolation and the 40-day period.