Question: Using this preamble:

```
\documentclass[pdftex,11pt,a4paper,openany]{memoir}
\usepackage[brazil]{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{indentfirst}
\usepackage{latexsym}
\usepackage{amsmath,amssymb,amsfonts,wasysym}
\usepackage[pdftex]{graphicx}
\usepackage{wrapfig}
\usepackage[left=3cm,right=2cm,top=3cm,bottom=3cm]{geometry}
\usepackage{color}
\usepackage[dvipsnames]{xcolor}
\definecolor{darkgray}{gray}{0.3}
\setcounter{secnumdepth}{3}
\setcounter{tocdepth}{3}
\usepackage[pdftex, colorlinks=true, linkcolor=darkgray, citecolor=blue, urlcolor=blue]{hyperref}

```

TexMaker gives this error message:

```
! LaTeX Error: Command \newfloat already defined.
Or name \end... illegal, see p.192 of the manual.

```

Where is the problem?

Answer: 
This is *almost* the same answer I posted to a related (identical?) question [here](https://tex.stackexchange.com/a/347965/103825). I am re-posting most of it here for the sake of those finding these posts via Google search.

There are two different solutions, one local and one global, using the `enumitem` package.

The idea for both is to use the `font=` key for `enumitem`.

**Local:** Every time you want an individual `enumerate` environment with bold numbers/letters/numerals (whatever the setting is), just use:

```
\begin{enumerate}[font=\bfseries]
*your code here*
\end{enumerate}

```

Note that this solution is *strictly* local -- the font settings will be *not* be inherited by `enumerate` environments contained/nested within outer `enumerate` environments for which the setting does not hold -- [see another of my related answers here](https://tex.stackexchange.com/a/347968/103825).

**Global:** If you know in advance that you will want *every* `enumerate` environment to have bold numbers/letters/numerals (whatever the setting is), then put the following in the document's preamble:

```
\setlist[enumerate]{font=\bfseries}

```

*Note:* As a general rule of thumb, it is preferable to use the `font=` key for `enumitem` (as opposed to the `label=` key suggested in other answers) if all you want to do is to make the numbers/letters/etc. bold. `label=` completely overwrites the standard settings of enumerate, while `font=` just modifies them.

---

Source: I read the [documentation](http://ctan.space-pro.be/tex-archive/macros/latex/contrib/enumitem/enumitem.pdf) for `enumitem`, and both of the above solutions worked for me using TeXstudio and XeLaTeX compiler.
By using `enumerate` package you can also use this command.

```
\documentclass{article}
\usepackage{enumerate}
\begin{document}
    \begin{enumerate}[\bfseries a.]
        \item one
        \item two
        \item three
    \end{enumerate}
\end{document}

```