What is a Regular Word™?

If a word has a certain property, I call it a Regular Word™.

You can use the examples below to find the property:

$$\begin{array}{|c|c|} \hline \bbox[yellow]{\textbf{Regular Words™}}&\bbox[yellow]{\textbf{Not Regular Words™}}\\ \hline \text{NAP}&\text{SLEEP}\\ \hline \text{AXED}&\text{FIRED}\\ \hline \text{QUIT}&\text{EXIT}\\ \hline \text{WHIZ}&\text{GENIUS}\\ \hline \text{DEATH}&\text{EXPIRY}\\ \hline \text{GREEK}&\text{LATIN}\\ \hline \text{BOXING}&\text{FIGHTING}\\ \hline \text{KIDNAP}&\text{ABDUCT}\\ \hline \text{OBJECT}&\text{THING}\\ \hline \text{REVIEW}&\text{PERUSE}\\ \hline \text{SPHINX}&\text{RIDDLER}\\ \hline \text{HEXAGON}&\text{PENTAGON}\\ \hline \text{MOSQUES}&\text{TEMPLES}\\ \hline \text{FEMINISM}&\text{EQUALITY}\\ \hline \text{LUXURIANT}&\text{LAVISH}\\ \hline \text{CONTEXTUAL}&\text{RELATED}\\ \hline \text{EXCAVATION}&\text{DIGGING}\\ \hline \text{JUXTAPOSES}&\text{OVERLAPS}\\ \hline \text{PERPLEXITY}&\text{CONFUSION}\\ \hline \text{INTOXICATES}&\text{INEBRIATES}\\ \hline \end{array}$$

For those without MathJax, or if you want to pop this into a spreadsheet, here is a CSV version:

Regular™,Not Regular™
NAP,SLEEP
AXED,FIRED
QUIT,EXIT
WHIZ,GENIUS
DEATH,EXPIRY
GREEK,LATIN
BOXING,FIGHTING
KIDNAP,ABDUCT
OBJECT,THING
REVIEW,PERUSE
SPHINX,RIDDLER
HEXAGON,PENTAGON
MOSQUES,TEMPLES
FEMINISM,EQUALITY
LUXURIANT,LAVISH
CONTEXTUAL,RELATED
EXCAVATION,DIGGING
JUXTAPOSES,OVERLAPS
PERPLEXITY,CONFUSION
INTOXICATES,INEBRIATES
• Sorry, but I didn't understand what exactly I have to solve. – BlackPanda Sep 23 '16 at 11:41
• @BlackPanda all the Regular words share a specific property/pattern which is not valid for the Not Regular words. You can look at older puzzles tagged word-property (click on the tag) for examples. – Maria Deleva Sep 23 '16 at 13:11
• @BlackPanda Read the tag wiki about word-property. – haykam Sep 24 '16 at 1:41
• Oh okay, so I had to define what a regular word is. Anyway it's solved. Thanks for the tip. – BlackPanda Sep 24 '16 at 15:39