+.Sh MACRO SYNTAX
+The
+.Nm
+macros are classified by scope: line scope or block scope.
+Line macros are only scoped to the current line (and, in some
+situations, the subsequent line).
+Block macros are scoped to the current line and subsequent lines until
+closed by another block macro.
+.Ss Line Macros
+Line macros are generally scoped to the current line, with the body
+consisting of zero or more arguments.
+If a macro is scoped to the next line and the line arguments are empty,
+the next line, which must be text, is used instead.
+Thus:
+.Bd -literal -offset indent
+\&.I
+foo
+.Ed
+.Pp
+is equivalent to
+.Sq \&.I foo .
+If next-line macros are invoked consecutively, only the last is used.
+If a next-line macro is followed by a non-next-line macro, an error is
+raised, except for
+.Sx \&br ,
+.Sx \&sp ,
+and
+.Sx \&na .
+.Pp
+The syntax is as follows:
+.Bd -literal -offset indent
+\&.YO \(lBbody...\(rB
+\(lBbody...\(rB
+.Ed
+.Bl -column "MacroX" "ArgumentsX" "ScopeXXXXX" "CompatX" -offset indent
+.It Em Macro Ta Em Arguments Ta Em Scope Ta Em Notes
+.It Sx \&AT Ta <=1 Ta current Ta \&
+.It Sx \&B Ta n Ta next-line Ta \&
+.It Sx \&BI Ta n Ta current Ta \&
+.It Sx \&BR Ta n Ta current Ta \&
+.It Sx \&DT Ta 0 Ta current Ta \&
+.It Sx \&I Ta n Ta next-line Ta \&
+.It Sx \&IB Ta n Ta current Ta \&
+.It Sx \&IR Ta n Ta current Ta \&
+.It Sx \&OP Ta 0, 1 Ta current Ta compat
+.It Sx \&R Ta n Ta next-line Ta \&
+.It Sx \&RB Ta n Ta current Ta \&
+.It Sx \&RI Ta n Ta current Ta \&
+.It Sx \&SB Ta n Ta next-line Ta \&
+.It Sx \&SM Ta n Ta next-line Ta \&
+.It Sx \&TH Ta >1, <6 Ta current Ta \&
+.It Sx \&UC Ta <=1 Ta current Ta \&
+.It Sx \&br Ta 0 Ta current Ta compat
+.It Sx \&fi Ta 0 Ta current Ta compat
+.It Sx \&ft Ta 1 Ta current Ta compat
+.It Sx \&in Ta 1 Ta current Ta compat
+.It Sx \&na Ta 0 Ta current Ta compat
+.It Sx \&nf Ta 0 Ta current Ta compat
+.It Sx \&sp Ta 1 Ta current Ta compat
+.El
+.Pp
+Macros marked as
+.Qq compat
+are included for compatibility with the significant corpus of existing
+manuals that mix dialects of roff.
+These macros should not be used for portable
+.Nm
+manuals.
+.Ss Block Macros
+Block macros comprise a head and body.
+As with in-line macros, the head is scoped to the current line and, in
+one circumstance, the next line (the next-line stipulations as in
+.Sx Line Macros
+apply here as well).
+.Pp
+The syntax is as follows:
+.Bd -literal -offset indent
+\&.YO \(lBhead...\(rB
+\(lBhead...\(rB
+\(lBbody...\(rB
+.Ed
+.Pp
+The closure of body scope may be to the section, where a macro is closed
+by
+.Sx \&SH ;
+sub-section, closed by a section or
+.Sx \&SS ;
+part, closed by a section, sub-section, or
+.Sx \&RE ;
+or paragraph, closed by a section, sub-section, part,
+.Sx \&HP ,
+.Sx \&IP ,
+.Sx \&LP ,
+.Sx \&P ,
+.Sx \&PP ,
+or
+.Sx \&TP .
+No closure refers to an explicit block closing macro.
+.Pp
+As a rule, block macros may not be nested; thus, calling a block macro
+while another block macro scope is open, and the open scope is not
+implicitly closed, is syntactically incorrect.
+.Bl -column "MacroX" "ArgumentsX" "Head ScopeX" "sub-sectionX" "compatX" -offset indent
+.It Em Macro Ta Em Arguments Ta Em Head Scope Ta Em Body Scope Ta Em Notes
+.It Sx \&HP Ta <2 Ta current Ta paragraph Ta \&
+.It Sx \&IP Ta <3 Ta current Ta paragraph Ta \&
+.It Sx \&LP Ta 0 Ta current Ta paragraph Ta \&
+.It Sx \&P Ta 0 Ta current Ta paragraph Ta \&
+.It Sx \&PP Ta 0 Ta current Ta paragraph Ta \&
+.It Sx \&RE Ta 0 Ta current Ta none Ta compat
+.It Sx \&RS Ta 1 Ta current Ta part Ta compat
+.It Sx \&SH Ta >0 Ta next-line Ta section Ta \&
+.It Sx \&SS Ta >0 Ta next-line Ta sub-section Ta \&
+.It Sx \&TP Ta n Ta next-line Ta paragraph Ta \&
+.El
+.Pp
+Macros marked
+.Qq compat
+are as mentioned in
+.Sx Line Macros .
+.Pp
+If a block macro is next-line scoped, it may only be followed by in-line
+macros for decorating text.
+.Ss Font handling
+In
+.Nm
+documents, both
+.Sx Physical markup
+macros and
+.Xr roff 7
+.Ql \ef
+font escape sequences can be used to choose fonts.
+In text lines, the effect of manual font selection by escape sequences
+only lasts until the next macro invocation; in macro lines, it only lasts
+until the end of the macro scope.
+Note that macros like
+.Sx \&BR
+open and close a font scope for each argument.
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