Template:Base quantities and count

Base quantity	Symbol for quantity	Symbol for dimension	Name of SI unit	Symbol for SI unit [*]
length	l	L	meter	m
mass	m	M	kilogram	kg
time	t	T	second	s
electric current	I	I	ampere	A
thermodynamic temperature	T	Θ	kelvin	K
amount of substance *,§	nX = NX·NA-1	N	mole	mol
count *,$	NX	X	counting-unit	x
unit-entity *,$	UX	U	counting-unit	x
charge *,€	QX = NX·zX·e	I·T	coulomb	C = A·s
luminous intensity	Iv	J	candela	cd

[*] »SI base units, except for the canonical 'counting-unit' [x]. The following footnotes are canonical comments.

^* For the quantities n, N, U, and Q, the entity-type X of the unit-entity U has to be specified in the text and indicated by a subscript: n_O2; N_ce; Q_X.

^§ Amount n_X is a counting quantity, converting the counting-unit [x] into moles [mol] using the Avogadro constant, N_A.

^$ Count N_X equals the number of unit-entities U_X. In the SI, the quantity 'count' is explicitly considered as an exception: "Each of the seven base quantities used in the SI is regarded as having its own dimension. .. All other quantities, with the exception of counts, are derived quantities" (Bureau International des Poids et Mesures 2019 The International System of Units (SI)). A unit-entity U_X is not a count (U_X is not a number of U_X). N_X has the dimension X of a count and U_X has the dimension U of a unit-entity, and both quantities have the same 'counting unit' [x].

^€ Charge is a derived SI quantity, included here for comparison. Charge is a counting quantity, converting the counting unit [x] into coulombs [C] using the elementary charge, e, or converting moles [mol] into coulombs [C] using the Faraday constant, F. z_X is the charge number of entity X, which is a constant for any defined entity X. Q_X = n_X·z_X·F