The tectogrammatical lemma of a node (further t-lemma) is one of the attributes of the node in a tectogrammatical tree (the t_lemma attribute). The value of the t_lemma attribute is either the node's lexical value (i.e. its basic form, represented as a sequence of graphemes), or an "artificial" value (the so called t-lemma substitute, see Section 4, "T-lemma substitutes").
Essentially, it is possible to distinguish two kinds of nodes according to their t-lemmas:
nodes representing lexical units present at the surface level of the sentence - the t-lemma of such a node is the basic form of the given lexical unit - and newly established nodes, which are copies of other nodes, present at the surface level (the t-lemmas of the copies are not different from the t-lemmas of the copied nodes, so there is no need to treat them differently),
newly established nodes with t-lemma substitutes
(Exceptions to this rough division are described below.)