<sub>This is in the spirit of the [What is a Word/Phrase™][1] series started by [JLee][2] with a special brand of [Phrase™][3] and [Word™][4] puzzles.</sub>

---
 
If a word conforms to a special rule, I call it a **Taggy Word™**.  
Use the following examples below to find the rule.


$$
% set Title text. (spaces around the text ARE important; do not remove.)
% increase Pad value only if your entries are longer than the title bar.
%
\def\Pad{\P{0.0}}  \def\Title{\textbf{ Taggy }}
%
\def\S#1#2{\Space{#1}{20px}{#2px}}\def\P#1{\V{#1em}}\def\V#1{\S{#1}{9}}
\def\T{\Title\textbf{Words}^{\;\!™}\Pad}\def\NT{\Pad\textbf{Not}\T\ }\displaystyle
\smash{\lower{29px}\bbox[palegreen]{\phantom{\rlap{rubio.2019.05.15}\S{6px}{0}
\begin{array}{cc}\Pad\T&\NT\\\end{array}}}}\atop\def\V#1{\S{#1}{5}}
\begin{array}{|c|c|}\hline\Pad\T&\NT\\\hline
%
\text{  ANIMAL }&\text{ CREATURE }\\ \hline
\text{  POET }&\text{ SINGER }\\ \hline
\text{  CROSS }&\text{ LASER }\\ \hline
\text{  LIAR }&\text{ HONEST }\\ \hline
\text{  NUMB }&\text{ SHRILL }\\ \hline
\text{  KNOW }&\text{ REALIZE }\\ \hline
\text{  LOG }&\text{ TREE }\\ \hline
\text{  FORM }&\text{ LOOK }\\ \hline
\text{  MATH }&\text{ DIVIDE }\\ \hline
\text{  ALTER }&\text{ CHANGING }\\ \hline
\text{  MYSTERY* }&\text{ STRANGE }\\ \hline
\end{array}$$
&emsp; &emsp; &emsp; &emsp; &emsp; &emsp; &emsp; &emsp; &emsp; &emsp; &emsp; &emsp; &emsp; &emsp; &emsp; &emsp; &emsp; &emsp; &emsp; &emsp; **\* This is a Very Taggy Word™**


And, if you want to analyze, here is a CSV version:

    Taggy Words™,Not Taggy Words™
    ANIMAL,CREATURE
    POET,SINGER
    CROSS,LASER
    LIAR,HONEST
    NUMB,SHRILL
    KNOW,REALIZE
    LOG,TREE
    FORM,LOOK
    MATH,DIVIDE
    ALTER,CHANGING
    MYSTERY,STRANGE

The puzzle satisfies the series' inbuilt assumption, that each word can be tested for whether it is a Taggy Word™ without relying on the other words.
These are not the only examples of Taggy Words™; many more exist.

**What is the special rule these words conform to?**  
**Why are they called Taggy Words™ and Very Taggy Words™?**

Good luck!

  [1]: https://puzzling.stackexchange.com/search?q=%22what+is+a%22+word+is%3Aquestion
  [2]: https://puzzling.stackexchange.com/users/463
  [3]: https://puzzling.stackexchange.com/search?q=%22Phrase%22%20user%3A463%20is%3Aquestion
  [4]: https://puzzling.stackexchange.com/search?q=%22What+is+%22+%22Word%22+-missing+user%3A463+is%3Aquestion