The second tone: rising tone, marked by an acute accent on top of the Pinyin vowal, such as á in má(麻, numb)
The third tone: falling-rising tone, marked by a caron (or rounded breve) on top of the Pinyin vowal, such as ă in mă(馬, horse)
The fourth tone: falling tone, marked by a grave accent on top of the Pinyin vowal, such as à in mà(罵, to scold)
The tone marks are important for correct pronunciation of Mandarin syllables. A common convention is to use a tone number at the end of individual syllables to mark their tones.
An umlaut is placed over the letter u when it occurs after the initials l and n in order to represent the sound yü. Tonal markers are added on top of the umlaut, as in lǜ and nǚ. v is commonly used instead by convention.