What this suffix does
-acious/-icious means "full of" or "having that quality" intensely: tenacious, audacious, vivacious, voracious, malicious, delicious.
ESEN
Suffix · forms adjectives
-acious / -icious
From Latin "-ax/-acis": means "full of" or "having the quality of" to a high degree. Tenacious, audacious, malicious, delicious.
In Spanish: -az / -ioso / -osoIntermediate
Written by Bryan López, English teacher · Updated
How it is formed
Latin root + acious (group A) or + icious (group B). The variant cannot be predicted: learn word by word.
- root + acious (intense quality, often positive or neutral)ten (hold) = tenaciousaud (dare) = audaciousviv (live) = vivaciousloqu (speak) = loquaciousvor (devour) = voracious
- root + icious (quality, often moral)mal (bad) = malicioussus (under) = suspiciousdel (delight) = deliciousambit = ambitiousvic (vice) = vicious
- root + acious/icious → noun in -acity/-icitytenacious → tenacityaudacious → audacityvoracious → voracitymalicious → malicesuspicious → suspicion
The two forms -acious and -icious are historically the same Latin ending at different stages of evolution into English. There is no rule to predict which to use: memorise by word. The corresponding noun usually ends in -acity, -icity or -ice.
How it is pronounced
-acious / -icious/eɪʃəs/ or /ɪʃəs/ · sounds like 'AY-shus' or 'IH-shus'
Tap the button to hear how the ending sounds. Each word in the table has its own audio.
Examples
Base word
With -acious / -icious
In a phrase
- ten (hold)tenaciousShe's tenacious. She never gives up, no matter how hard things get.
- aud (dare)audaciousIt was an audacious move, but it actually worked.
- viv (live)vivaciousMy aunt is so vivacious, she lights up every room she walks into.
- vor (devour)voraciousHe's a voracious reader. He finishes a book every week.
- loqu (speak)loquaciousOur tour guide was very loquacious. He talked the whole trip.
- mal (bad)maliciousSomeone left a malicious comment on her photo, so she deleted it.
- sus (under)suspiciousThe neighbors got suspicious when they saw a strange car parked outside.
- del (delight)deliciousThis cake is delicious. Can I have another piece?
- vic (vice)viciousBe careful, that dog can be vicious with strangers.
- sag (perceive)sagaciousHer grandfather was a sagacious old man who always gave good advice.
Common mistakes
confusing "suspicious" and "malicious"
"suspicious" = generating or harbouring suspicion; "malicious" = having deliberate harmful intent
"suspicious" can apply to someone who suspects ("I am suspicious of him") or to what arouses suspicion ("suspicious behaviour"). "malicious" implies intent to harm: "a malicious lie" = a lie told with intent to hurt.
"vicious" = addicted to vices
"vicious" = fierce, violent, cruel, or a vicious circle
In modern English "vicious" primarily means fierce, violent or cruel: "a vicious attack", "a vicious dog". Also: "vicious cycle/circle" = círculo vicioso. Not primarily used for addictions.
audacious = always positive
audacious = daringly bold in a way that can be impressive or shocking
"audacious" can be a compliment ("an audacious creative vision") or a rebuke ("the audacity of the claim"). The boldness it implies can be admired or censured depending on context.
A trick to remember it
Picture the quality turned up to the MAX, like raising the volume: audACIOUS = audacity at its peak. voracIOUS = hunger at its peak. All of them describe a trait taken to the extreme.
Practise what you learned
Exercise 1 · Form the word
Exercise 2 · Pick the right one
What is the difference between "suspicious" and "malicious"?
Exercise 3 · Pick the right one
"Tenacious" describes someone who...
Frequently asked questions
What does the suffix -acious / -icious mean in English?
The suffix -acious / -icious from Latin "-ax/-acis": means "full of" or "having the quality of" to a high degree. Tenacious, audacious, malicious, delicious. In Spanish it usually maps to -az / -ioso / -oso.
How do you pronounce -acious / -icious?
The ending -acious / -icious is pronounced /eɪʃəs/ or /ɪʃəs/ · sounds like 'AY-shus' or 'IH-shus'. For example, "tenacious".
Can you give an example of a word with -acious / -icious?
"ten (hold)" becomes "tenacious". It is a typical example of the -acious / -icious suffix.
Other useful suffixes
-esque
From Italian "-esco": means "in the style of" or "reminiscent of". Kafkaesque, picturesque, grotesque.
-itude
From Latin "-itudo": forms abstract nouns of state or quality. Solitude, gratitude, magnitude, fortitude.
-ous / -ious
Turns a noun into an adjective meaning "full of" or "having that quality": danger becomes dangerous.
Learn every English suffix
-tion, -ness, -ful, -ly, -able... every ending you need to understand thousands of words at once.