intrados
rise
spandril
extrados
perpendicular distance between intra-dos and extrados
vertical distance between springing line and intrados
perpendicular distance between springing line and extrados
none of the above
haunch
voussoirs
skewbacks
arches require more headroom to span the openings like doors, windows etc.
arches require strong abutments to withstand arch thrust
arches are difficult in construction
all of the above
centring
actual laying of arch work
striking of centring