directrix

English

Alternative forms

• directrice

Etymology

Learned borrowing from Latin dīrēctrīx. By surface analysis, direct +‎ -trix.

Pronunciation

• enPR: dĭ-rĕk′trĭks, dī-
• (Received Pronunciation) IPA^(key): /dɪˈɹɛk.tɹɪks/, /-ˈɹek-/; /daɪ̯-/, /dʌɪ̯-/
• (General American, Canada) IPA^(key): /dɪˈɹɛk.tɹɪks/; /daɪ̯-/

  • Audio (US):

    (file)

• (Australia) IPA^(key): /dɪˈɹek.tɹɪks/; /dɑe̯-/
• (New Zealand) IPA^(key): /dəˈɹek.tɹəks/; /dɑe̯-/
• (Scotland) IPA^(key): /dɪˈɹɛk.tɹɪks/; /dʌi̯-/, /dəi̯-/
• Rhymes: -ɛktrɪks
• Hyphenation: di‧rec‧trix

Noun

In this picture of an ellipse, a parabola, and an hyperbola, the black line is their shared directrix.

directrix (plural directrixes or directrices)

1. Female equivalent of director.
2. (geometry) A line used to define a curve or surface; especially a line, the distance from which a point on a conic has a constant ratio to that from the focus.

Derived terms

• conic section directrix
• graph directrix
• ruled surface directrix

Translations

a female who directs — see directress

a line used to define a curve or surface

• Dutch: richtlijn (nl) m or f
• Finnish: johtosuora
• French: directrice (fr) f
• Greek: διευθετούσα (el) f (diefthetoúsa)
• Polish: kierownica (pl) f
• Spanish: directriz (es) f
• Tamil: இயக்குவரை (ta) f (iyakkuvarai)

References

• “directrix, n.”, in OED Online ⁠, Oxford: Oxford University Press, 2025.

Further reading

• “directrix”, in OneLook Dictionary Search.

Anagrams

• creditrix

Latin

Etymology

From dīrēctus + -trīx.

Pronunciation

• (Classical Latin) IPA^(key): [diːˈreːk.triːks]
• (modern Italianate Ecclesiastical) IPA^(key): [diˈrɛk.triks]
• Hyphenation: dī‧rēc‧trīx

Noun

dīrēctrīx f (genitive dīrēctrīcis, masculine dīrēctor); third declension

1. female equivalent of dīrēctor
   • 1141 – 1445, Liber Pluscardensis VII.14 (ed. F. J. H. Skene (Historians of Scotland VII) [Edinburgh 1877], quoted in DMLBS):

     Grecia […], scienciārum inventrīx […], mīlicie et armōrum flōs et dīrēctrīx

     Greece […], the inventor of the sciences […], the flower and guide of warfare and arms

   • c. 1446, Pseudo-Elmham, Vita et gesta Henrici V 91.107 (ed. T. Hearne [Oxford 1727], quoted in DMLBS):

     rēgis Anglōrum […] prūdenciā dīrēctrīce

     the king of the English […] with prudence as his guide

   • c. 1446, Pseudo-Elmham, Vita et gesta Henrici V 91.251 (ed. T. Hearne [Oxford 1727], quoted in DMLBS):

     quod pūnctuāciōnēs previe, in concordiam dīrēctrīcēs, per persōnālem rēgis presenciam fīnālem sortīrentur effectum

     that the previous points, acting as guides for the agreement, should reach their final effect through the personal presence of the king

Declension

Third-declension noun.

	singular	plural
nominative	dīrēctrīx	dīrēctrīcēs
genitive	dīrēctrīcis	dīrēctrīcum
dative	dīrēctrīcī	dīrēctrīcibus
accusative	dīrēctrīcem	dīrēctrīcēs
ablative	dīrēctrīce	dīrēctrīcibus
vocative	dīrēctrīx	dīrēctrīcēs

Further reading

• R. E. Latham, D. R. Howlett, & R. K. Ashdowne, editors (1975–2013), “directrix”, in Dictionary of Medieval Latin from British Sources‎^[1], London: Oxford University Press for the British Academy, →ISBN, →OCLC