I am using LuaLaTeX and `babel` to typeset a document in Hebrew with some text in English.

The roman font (main font) for Hebrew will be David CLM, but I want some text to be typed in font Arial. What is the correct way to do that?

What I have now is the following:

```
% !TEX TS-program = lualatex
\documentclass{book}
\usepackage[hebrew,provide=*,bidi=default]{babel}
\usepackage{fontspec}
\babelfont[hebrew]{rm}[Script=Hebrew]{David CLM}
\babelfont[hebrew]{arial}[Script = Hebrew]{Arial}
% Following example \babelfont{kai}{FandolKai} in babel manual
\begin{document}
אבג דהו
\textarial{בדיקה}
\end{document}
```

Until now I was using XeTeX and polyglossia with fontspec, and I used to introduce a new font family with `\newfontfamily\arial{Arial}[Script=Hebrew]` and then `{\arial 〈some text in Hebrew〉}`.

Following the example on page 18 of the babel manual (`\babelfont{kai}{FandolKai}` example), why babel defines new macros `arialfamily` and `textarial` but not `arialdefault`? I think that `\arial {text}` is the most intuitive, why babel developers think different?

In the babel documentation it says that

> Babel has native support for Unicode fonts (OpenType and TrueType) in luatex and xetex by means of a high level interface on top of fontspec.

What does it mean "high level interface"? That `\babelfont` is more agile that `\newfontfamily` and other fontspec macros?