creating a new environment

Question

I want to create a new environment that uses a counter which automatically numbers the sentences in my document.

For example,

Definiton 1.1. lorem ipsum dolor amet. Definiton 1.2. The quick brown fox...

And so on...

Answer 1

\newcounter{defn}[section]
\newenvironment{defn}{%
   \refstepcounter{defn}%
   \textbf{Definition \thedefn}
  }{%
}

...

\begin{defn}
lorem ipsum dolor emt.
\end{defn}
\begin{defn}
The quick brown fox...
\end{defn}