| SNELLSLAW | In optics, a formula concerning the angles of incidence and refraction |
| EPIDEMIOLOGY | Study of the incidence and distribution of diseases |
| EPIDEMIOLOGIST | Person who studies the incidence and distribution of disease (14) |
| ABERRATION | In optics, a defect in a lens or mirror that causes the formation of either a distorted image or one with coloured fringes |
| TACKS | Temporary basting stitches in dressmaking, tailoring and drapery; drawing pins; or, ropes regulating the angles of sails in relation to wind direction (5) |
| GANTRY | Area behind a bar where bottles are mounted in optics; a stand for barrels; or, a structure supporting a crane, railway signal or road sign (6) |
| EYEPIECE | In optics, a bit of looker? (8) |
| DEGREES | The angles of letters (7) |
| NEPAL | Its constitution contains the phrase "on the five angles of the flag the external angles will be equal to the internal angles" |
| AXIL | In botany, the angle of divergence between the upper side of a branch, leaf, or petiole, and the stem or branch from which it springs (4) |
| EQUILATERAL | The type of triangle with sides of the same length and internal angles of the same magnitude |
| ERATOSTHENES | Greek mathematician and astronomer who calculated the circumference of the earth by observing the angle of the sun's rays (12) |
| COSINE | Function of the angle of a triangle to the lengths of its sides (6) |
| SLANT | The angle of a strip of wood around the North (5) |
| TRIGONOMETRY | The branch of mathematics concerned with calculating the angles and sides of triangles (12) |
| EIGHT | The number of sides and angles of an octagon (5) |
| ICOSAGON | In geometry, a plane figure with twenty sides and internal angles of 162degrees (8) |
| CORONER | Nothing in the angle of a room for court official |
| FLUORIDE | Anion added to water supplies to reduce the incidence of tooth decay in the population (8) |
| ISOGRAM | Line on a map connecting points having equal incidence of a particular feature |
