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Nonterminal symbols are those symbols that can be replaced. They may also be called simply syntactic variables.A formal grammar includes a start symbol, a designated member of the set of nonterminals from which all the strings in the language may be derived by successive applications of the production rules.
It can also be used with highly specific meanings in specialised contexts. In the description of protein structure, in particular in the Protein Data Bank file format, a heteroatom record (HETATM) describes an atom as belonging to a small molecule cofactor rather than being part of a biopolymer chain.
Typographical symbols and punctuation marks are marks and symbols used in typography with a variety of purposes such as to help with legibility and accessibility, or to identify special cases.
A nonterminal symbol is called productive, or generating, if there is a derivation for some string of terminal symbols. X {\displaystyle X} is called reachable if there is a derivation S ⇒ ∗ α X β {\displaystyle S{\stackrel {*}{\Rightarrow }}\alpha X\beta } for some strings α , β {\displaystyle \alpha ,\beta } of nonterminal and ...
A context-sensitive grammar is a noncontracting grammar in which all rules are of the form αAβ → αγβ, where A is a nonterminal, and γ is a nonempty string of nonterminal and/or terminal symbols. However, some authors use the term context-sensitive grammar to refer to noncontracting grammars in general. [1]
A chemical element, often simply called an element, is a type of atom which has a specific number of protons in its atomic nucleus (i.e., a specific atomic number, or Z). [ 1 ] The definitive visualisation of all 118 elements is the periodic table of the elements , whose history along the principles of the periodic law was one of the founding ...
The N-terminus is the first part of the protein that exits the ribosome during protein biosynthesis.It often contains signal peptide sequences, "intracellular postal codes" that direct delivery of the protein to the proper organelle.
The large majority of an atom's mass comes from the protons and neutrons that make it up. The total number of these particles (called "nucleons") in a given atom is called the mass number. It is a positive integer and dimensionless (instead of having dimension of mass), because it expresses a count.