cid
Latincut, kill
About This Root
Picture a Roman with a blade. The Latin verb caedere meant to strike with a sharp edge — to cut, to fell, to kill. Its present stem shows up as -cid- and its past-participle stem as -cis-, and English inherited both. From that single swing of the blade, two great branches grew, and the prefix tells you what the blade is doing.
The killing branch lives in the suffix -cide, which names either the act of killing or the thing that does the killing. Here the prefix names the victim: sui- (oneself) + cide = suicide; homo- (a human being, from Latin homo) + cide = homicide; geno- (a race or people) + cide = genocide; patri- (father) + cide = patricide. Modern chemistry borrowed the same machine to coin product names — pest + i + cide = pesticide, herb + i + cide = herbicide, insect + i + cide = insecticide, fungi + cide = fungicide, bacteri + cide = bactericide. In every one, -cide is the killer; the front of the word is what gets killed.
The cutting branch lives in -cise/-cis, and here the prefix tells you how the cut is made. prae- (before, in front) + cis = precise: cut off right at the front, trimmed to the exact edge — nothing extra. con- (thoroughly) + cis = concise: cut down to the essentials. in- (into) + cis = incise, incision: a cut made into a surface, as a surgeon's cut into skin; the incisor is the front tooth that cuts. ex- (out) + cis = excise, excision: to cut something out and remove it. The scissors are the two-bladed tool that cuts, and even chisel traces back through Old French to caedere — the blade that cuts stone and wood.
Between the two branches sits the most useful word of all: decide. de- (off, away) + caedere = to 'cut off' — and what you cut off are all the other choices. When you decide, you take a knife to a branching set of options and sever every path but one. That is why a decisive person is one who cuts cleanly, and why someone who is undecided is still standing at the fork with the knife unraised.
A caution: cid (caedere, cut/kill) is not the same root as cad (cadere, to fall), even though English spelling pushes them together in words like incident and coincidence. Those belong to falling, not cutting. Same neighborhood, different family.
See a blade coming down. -cide names what it kills (suicide, pesticide); -cise/-cis names how it cuts (precise = cut to the exact edge, incise = cut in, excise = cut out). And to decide is to cut off every option but one.
Core Words Deep Dive
The few words from this family worth telling in full — one by one.
decideThe teaching gem of this root.
The teaching gem of this root. de- (off) + caedere (cut) literally means 'to cut off' — and what gets cut off are all the rival options. Imagine a branching set of paths; deciding is taking a blade to them and severing all but one. This is why decisive means clean and quick with the cut, and indecision is standing frozen with the knife still up. Most learners never connect decide to homicide, yet they share the same Latin blade.
Open decidepreciseprae- (in front) + cis (cut) = 'cut off at the front,' trimmed exactly to the edge with nothing hanging over.
prae- (in front) + cis (cut) = 'cut off at the front,' trimmed exactly to the edge with nothing hanging over. That image — a clean, deliberate cut leaving no excess — became the meaning 'exact, with no margin of error.' Compare concise, which is con- (thoroughly) + cis: cut all the way down to the essentials.
Open precisesuicidesui- (of oneself, from Latin sui) + cide (killing) = the killing of oneself.
sui- (of oneself, from Latin sui) + cide (killing) = the killing of oneself. It is the clearest template for the whole -cide family: swap the victim at the front and you get homicide (a human), genocide (a people), patricide (one's father). The suffix -cide is constant; the prefix names who dies.
Open suicidepesticidepest (a harmful creature) + -i- (connector) + cide (killer) = a substance that kills pests.
pest (a harmful creature) + -i- (connector) + cide (killer) = a substance that kills pests. This is the modern, industrial use of the root: chemists used -cide like a factory stamp to name killers of whole categories — herbicide kills plants, insecticide kills insects, fungicide kills fungi, bactericide kills bacteria. Here -cide means 'killer-of,' a thing rather than a deed.
Open pesticideincisionin- (into) + cis (cut) + -ion (act) = the act or result of cutting into something, most often a surgeon's deliberate cut into skin.
in- (into) + cis (cut) + -ion (act) = the act or result of cutting into something, most often a surgeon's deliberate cut into skin. The same in- + cis gives incise (to cut into / engrave) and incisor (the front tooth that cuts food). Contrast excision: ex- (out) + cis = cutting something out and removing it.
Open incisionRelated Roots
cid (caedere) means cut/kill: decide, precise, homicide, pesticide. cad (cadere) means fall: accident, incident, coincidence, cadence. They look almost identical in spelling and both surface as -cid- in some words, but they are unrelated. Quick test: a blade is involved → cid; something drops or happens → cad.
Both relate to cutting, but sect (secare) is the everyday 'cut into parts' root — section, dissect, bisect, insect (an animal 'cut into' segments). cid/cis (caedere) carries the sharper edge of cutting off, cutting out, or striking dead: excise, incision, homicide. Dividing into pieces → sect; severing or killing → cid.
Associated Words · 44
decide
to make a choice or come to a conclusion
decision
a choice made after thinking about options
suicide
The act of intentionally killing oneself; a person who has done so
precisely
In an exact and accurate manner; exactly right
precise
Exact and accurate in every detail
homicide
The killing of one person by another; a person who kills
pesticide
A chemical used to kill harmful insects or pests
precision
The quality of being exact and accurate
decisive
Having a conclusive effect; able to make firm decisions quickly
genocide
The deliberate mass destruction of an ethnic or national group
decidedly
Clearly and without doubt; in a resolute manner
suicidal
Relating to or likely to commit suicide; extremely dangerous or self-destructive
scissors
A tool with two blades used for cutting
undecided
Not yet settled or resolved; not having made up one's mind
decisively
In a firm and resolute manner
incision
A cut made into something, especially a surgical cut
herbicide
A chemical used to kill unwanted plants
insecticide
A chemical substance used to kill insects
concise
Brief yet complete; expressing much in few words
chisel
A sharp-bladed tool for cutting stone, wood, or metal; to cut with such a tool
excise
A domestic tax on goods; to impose such a tax or remove by cutting
indecision
Inability to make a decision
excision
Surgical removal of tissue; deletion of text
imprecise
Not exact or accurate; vague