Definition of subtend in English:

subtend

verb

[with object]
• 1Geometry
(of a line, arc, or figure) form (an angle) at a particular point when straight lines from its extremities are joined at that point.

‘the angle subtended by a string of length r at the centre of the sphere’
• ‘The radian is a unit which connects the radius of an arc, the length of the arc and the angle subtended by the arc.’
• ‘The most common geometry for curved crystal diffraction is based on the Rowland circle principle, which relies on the well-known property of a circle that an arc segment subtends a constant angle for any point on the circle.’
• ‘Reticles are in the second focal plane, so as power is changed the angle subtended by the space between lines varies.’
• ‘In other words, when two plates subtended the same angle - one big and far away, the other small and nearby - the antennae also made the same angle with each other.’
• ‘The space between the dot and the first letter of the prime to the right of fixation subtended a visual angle of 21.’
1. 1.1(of an angle or chord) have bounding lines or points that meet or coincide with those of (a line or arc).
• ‘This allowed him to calculate the chord subtended by angles of 36, 72, 60, 90 and 120.’
• ‘The Arc, Chord, Radius, Height, Angle, Apothem, and Area Suppose you have a segment of a circle, bounded by an arc of the circle and the chord subtending it.’
• ‘In fact Shen demonstrated a remarkable ability to view spatial arrangements and he gave an approximate formula for the length of a circular arc in terms of the chord subtending the arc.’
• ‘Two pairs of parallel sides form equal inscribed angles that are bound to subtend equal chords - the third sides.’
• ‘These angles are subtended by the same chord, AW.’
• 2Botany
(of a bract) extend under (a flower) so as to support or enfold it.

‘the main beauty is provided by the bracts which subtend the flowers’
• ‘All flowers are subtended by a bract and two bracteoles.’
• ‘The flower meristems are produced acropetally by the inflorescence meristem and are subtended by bracts.’
• ‘The bract immediately subtends the sepal, partly enclosing it.’
• ‘Trillium species are characterized by a single trimerous flower subtended by a whorl of three leaves.’
• ‘A single flower is borne on a scape arising between the basal leaves and subtended by a large, leaf-like bract.’

Origin

Late 16th century (in subtend (sense 1)): from Latin subtendere, from sub- ‘under’ + tendere ‘stretch’. subtend (sense 2) dates from the late 19th century.

/sʌbˈtɛnd/