Hello, I don't understand why this macro works with this simple example but return the following error if I use it for chapters in my book. Thanks Fabrice %%%% \setupbodyfont [newcomputermodern-book,11pt] \unexpanded\def\N{\math{\mathbb{N}}\autoinsertnextspace} \defineenumeration [test] [title=yes, text={Test}, style=italic] \starttext \N \starttest \m{\forall n \in \N} \stoptest \stoptext %%%% tex error > tex error on line 64 in file ./terminale_suites_2.tex: Use of \N doesn't match its definition Soient \u, \v deux suites définies sur \N, \m{l} et \m{l'} deux réels. 54 \startitem 55 \u converge vers \m{l}, 56 \stopitem 57 \stopitemize 58 alors \m{l\geqslant 0}. 59 \stopproposition 60 \startremarque 61 Nous retiendrons que le passage à la limite sur une inégalité stricte restitue une inégalité large. 62 \stopremarque 63 \startcorollaire 64 >> Soient \u, \v deux suites définies sur \N, \m{l} et \m{l'} deux réels. 65 66 Si 67 68 \startitemize 69 \startitem 70 les suites \u et \v convergent respectivement vers \m{l} et \m{l'}, 71 \stopitem 72 \startitem 73 \m{\forall n \in\mathbb{N}, \thinspace u_n>v_n}, 74 \stopitem If you say, e.g., '\def\a1{...}', then you must always put '1' after '\a', since control sequence names are made up of letters only. The macro here has not been followed by the required stuff, so I'm ignoring it. mtx-context | fatal error: return code: 256 %%%%