ascender
/əˈsendə(r)/noun
1- a person or thing that ascends, in particular上升的人（或物）, 尤指：
1.1
- a part of a letter that extends above the level of the top of an x (as in b and f)字母中高于x的部分 （如在字母b和f中）。
1.2
- a letter having such a part有高于x部分的字母。
1.3
- Climbing a device which can be clipped to a rope to act as a foothold or handhold, or to keep something in position【登山】上升器。