Usted buscó: usepackage (Portugués - Inglés)

\\ usepackage{ xltxtra}
\\usepackage{xltxtra}

importação de pacote -\\ usepackage {}
package import - \\usepackage{}

carregamento do pacote biblatex -\\ usepackage{ biblatex}
load biblatex package - \\usepackage{biblatex}

\\ usepackage{ ucs}\\ usepackage[ utf8x] {inputenc}
\\usepackage{ucs} \\usepackage[utf8x]{inputenc}

\\ usepackage[ pdftex] {graphicx}\\ usepackage{ epstopdf}
\\usepackage[pdftex]{graphicx} \\usepackage{epstopdf}

todas as opções indicadas no comando\\ documentclass que sejam desconhecidas para a classe de documento seleccionada são passadas para os pacotes carregados com o\\ usepackage.
any options given in the \\documentclass command that are unknown by the selected document class are passed on to the packages loaded with \\usepackage.

\\ documentclass[ a4paper, 10pt] {article}\\ usepackage{ amssymb}\\ input{ definitions}%\\ begin{ document}\\ pagestyle{ empty}%\\ begin{ neededpkgs} {amssymb}\\ mathcommand {\\ surd}\\ pkgs{ amsmath}\\ mathcommand [\\ ddddot {}] {\\ ddddot{ a}}\\ mathcommand {\\ angle}\\ end{ neededpkgs}\\ command {\\ "a}\\ mathcommand {\\ exists}\\ mathcommand [\\ stackrel {} {}] {\\ stackrel{ abc} {=}}%\\ begin{ neededpkgs} [russian, koi8- r, t2c,] {babel, inputenc, fontenc, mathtext}%%\\ end{ neededpkgs}% isto iria necessitar de incluir os pacotes%\\ usepackage{ mathtext}%\\ usepackage[ t2c] {fontenc}%\\ usepackage[ russian] {babel}%\\ usepackage[ koi8- r] {inputenc}% just to explain the format\\ end{ document}
\\documentclass[a4paper,10pt]{article} \\usepackage{amssymb} \\input{definitions}% \\begin{document} \\pagestyle{empty}% \\begin{neededpkgs}{amssymb} \\mathcommand{\\surd} \\pkgs{amsmath}\\mathcommand[\\ddddot{}]{\\ddddot{a}} \\mathcommand{\\angle} \\end{neededpkgs} \\command{\\"a} \\mathcommand{\\exists} \\mathcommand[\\stackrel{}{}]{\\stackrel{abc}{=}} %\\begin{neededpkgs}[russian, koi8-r, t2c, ]{babel, inputenc, fontenc, mathtext}%% \\end{neededpkgs}% this would need to include the packages% \\usepackage{mathtext}% \\usepackage[t2c]{fontenc}% \\usepackage[russian]{babel}% \\usepackage[koi8-r]{inputenc}% just to explain the format \\end{document}