Fonts in OSX
dFont

The OSX TrueType format.
They come as a single file, which may include several styles

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DFONT2


TrueType

The original OS 9 (or previous) format.
Fonts with the TTF extension are seen as Windows TT fonts regardless of their platform
If you have not installed any other fonts, or any other programs (such as Adobe programs) you will only have dFonts and Truetype fonts.
Some of the newer TrueType fonts, such as Apple's dFonts may have extended character sets so may be completely different from older versions even if the font name is the same
At one time it was not advised to use TrueType fonts in layouts intended for commercial printing. In fact Headley Brothers specifications have never disallowed TrueType fonts. They may have caused problems in some older RIPs (Raster Image Processors) about ten years ago, but modern RIPs should not have the same problems. There are, of course, "bad" fonts of all flavours that can cause problems at output. It is advisable to use only quality fonts.

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TTF


PostScript-based Fonts

There are two major formats: Type 1 and Type 3
Most modern fonts, including Adobe fonts, are Type 1
Some very old fonts or graphic fonts may be Type 3. Type 3 fonts do not offer the best quality
Another variation of Type 1 fonts is Multiple master Fonts. I do not recommend their use. It is best to switch to OpenType fonts
All PostScript fonts come in two parts: screen fonts and printer fonts; both are required
Screen fonts styles (plain, bold, italic, etc) are usually combined into a single suitcase. Printer fonts always come as a single file per style

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OpenType

A relatively new font format developed by Adobe and Microsoft. OpenType is cross-platform between Windows and Macintosh computers.
OT fonts come as a single file per style and do not use separate screen fonts
OpenType is a file format, not a font technology – so they can be either modified PostScript fonts or modified TrueType fonts. Adobe's versions are modified PostScript, Microsoft's are usually modified TrueType
Adobe OpenType Pro fonts can contain advanced character sets (up to 65,536 glyphs). Older programs may only be able to use the first 256 glyphs (or may not be able to use them at all).
Adobe OpenType Std fonts are converted PostScript fonts and only have the standard 256 glyphs

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