Apex (diacritic)
Forgetting the apex, modern Latin spelling has recently started marking long vowels by using the macron. The macron is a sign that had always been used, and still is, to mark metrically long syllables (more recently called heavy syllables). This has caused confusion between syllable and vowel length in Latin, and most western dictionaries still cannot describe the nature of Latin vowels properly because of this. To make even more confusion, the acute accent is sometimes used in Latin to mark stressed syllables, just like in Spanish, when the macron is not used.