# How to make running lines in a list begin where just after the label?

I have problems with my custom list and the space from the leftmargin:

in order to illustrate,

I do not understand why [*] does not begin at the labelwidth which must be 1<><><><> long by definition. You can change the number of <> to see the listparindent is invariable....

What I want is that all the coloured arrows being where the blue one begins. I also want to put the label 1<><><><> at say a unknown value X cm [say 2cm] from the leftmargin. I do not care where the text actually begins.

I have a MWE:

%\RequirePackage{fix-cm}
\documentclass[twoside, a4paper, 11pt]{article}

\newcounter{list1}
\setcounter{list1}{0}

\newenvironment{mylist}

% level = 0
\begin{list}
{
{\arabic{list1}<><><><>}
}
{
%\let\makelabel\descriptionlabel
%\setlength{\labelwidth}{0ex}
%\setlength{\leftmargin}{\leftmargini}
\setlength{\rightmargin}{0ex}
\setlength{\labelsep}{0cm}
\setlength{\itemindent}{1\parindent}
%\setlength{\listparindent}{\labelwidth}
\setlength{\listparindent}{1\parindent}
\setlength{\itemsep}{0ex}
\setlength{\topsep}{0\parskip plus 0.5\parskip minus 0.5\parskip}
\setlength{\parsep}{1\parskip plus 0.5\parskip minus 0.5\parskip}
\setlength{\partopsep}{0\parskip}
\usecounter{list1}
}

\begin{document}

\small

here are many font families e.g. Computer Modern, Times, Arial and Courier. Those families can be grouped into three main categories: roman (rm) or serif, sans serif (sf) and monospace (tt) (see Typeface for more details). Each font family comes with the default design which falls into one of those categories
\begin{mylist}
\item  However, it is interchangeable among them. Computer Modern Roman is the default font family for LaTeX. Fonts in each family also have different properties (size, shape, weight, etc.). Families are meant to be consistent, so it is highly discouraged to change fonts individually rather than the whole family.

[*]However, it is interchangeable among them. Computer Modern Roman is the default font family for LaTeX. Fonts in each family also have different properties (size, shape, weight, etc.). Families are meant to be consistent, so it is highly discouraged to change fonts individually rather than the whole family.
\item However, it is interchangeable among them. Computer Modern Roman is the default font family for LaTeX. Fonts in each family also have different properties (size, shape, weight, etc.). Families are meant to be consistent, so it is highly discouraged to change fonts individually rather than the whole family.
\end{mylist}
However, it is interchangeable among them. Computer Modern Roman is the default font family for LaTeX. Fonts in each family also have different properties (size, shape, weight, etc.). Families are meant to be consistent, so it is highly discouraged to change fonts individually rather than the whole family.

\end{document}

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Your original definition has errors: you are defining an environment, but didn't provide the correct syntax for the start part and forgot the end part.

I'd suggest you to use the enumitem package to easily define your list:

\documentclass[twoside, a4paper, 11pt]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{enumitem}

\newlist{mylist}{enumerate}{2}
\setlist[mylist,1]{label=\arabic*<><><><>,leftmargin=*}

\begin{document}

\small

here are many font families e.g. Computer Modern, Times, Arial and Courier. Those families can be grouped into three main categories: roman (rm) or serif, sans serif (sf) and monospace (tt) (see Typeface for more details). Each font family comes with the default design which falls into one of those categories
\begin{mylist}
\item  However, it is interchangeable among them. Computer Modern Roman is the default font family for LaTeX. Fonts in each family also have different properties (size, shape, weight, etc.). Families are meant to be consistent, so it is highly discouraged to change fonts individually rather than the whole family.

[*]However, it is interchangeable among them. Computer Modern Roman is the default font family for LaTeX. Fonts in each family also have different properties (size, shape, weight, etc.). Families are meant to be consistent, so it is highly discouraged to change fonts individually rather than the whole family.
\item However, it is interchangeable among them. Computer Modern Roman is the default font family for LaTeX. Fonts in each family also have different properties (size, shape, weight, etc.). Families are meant to be consistent, so it is highly discouraged to change fonts individually rather than the whole family.
\end{mylist}
However, it is interchangeable among them. Computer Modern Roman is the default font family for LaTeX. Fonts in each family also have different properties (size, shape, weight, etc.). Families are meant to be consistent, so it is highly discouraged to change fonts individually rather than the whole family.

\end{document}


Using labelindent=<length> (as in labelindent=3cm) and possibly changing leftmargin=* to leftmargin=<length> (as in leftmargin=4cm), if required, you can obtain the result you required in the second part of your question.

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