Получить объект термина по tid
$term = taxonomy_term_load($tid);
Получить дерево словаря
taxonomy_get_tree($vid, $parent = 0, $max_depth = NULL, $load_entities = FALSE)
$vid Which vocabulary to generate the tree for.
$parent The term ID under which to generate the tree. If 0, generate the tree for the entire vocabulary.
$max_depth The number of levels of the tree to return. Leave NULL to return all levels.
$load_entities If TRUE, a full entity load will occur on the term objects. Otherwise they are partial objects queried directly from the {taxonomy_term_data} table to save execution time and memory consumption when listing large numbers of terms. Defaults to FALSE.