cidro -dro- gismu

x1 is a quantity of/contains/is made of hydrogen (H); [metaphor: light, flammable].

See also gapci, xukmi.

In notes:

gapci
x1 is gaseous/fumes/a gas/vapor of material/composition including x2, under conditions x3.
xukmi
x1 is an instance of substance/chemical/drug x2 (individual or mass) with purity x3.
cmuxu'i
x1 is an element of kind x2 with purity x3.
nikyjoijimjoibordrokemdicysro
s1 is a nickel–metal hydride battery in containment s3.
rakle
x1 is an atomic element in group x2 [usually, vertical column; denotes electron configuration and, thereby, chemical similarity with vertical neighbors] and period x3 [usually, horizontal row; denotes similarity in size with horizontal neighbors, as well as having the same number and type of electron shells as them] and belonging to other 'class'/'category'/'type'/having other properties x4 according to scheme/organization pattern/standard/periodic table x5.
ratniklesi
x1 is an atomic element in group x2 [usually, vertical column; denotes electron configuration and, thereby, chemical similarity with vertical neighbors] and period x3 [usually, horizontal row; denotes similarity in size with horizontal neighbors, as well as having the same number and type of electron shells as them] and belonging to other 'class'/'category'/'type'/having other properties x4 according to scheme/organization pattern/standard/periodic table x5.
dropanra zei ionti
x1 is a hydrogenic ion of element/isotope x2; x1 is isoelectronic to/with hydrogen; x1 is an x2 atom with exactly one electron
xipfne
x1 emits light characteristic of/is of the color that is described by/(as) arising from/associated with the approximately twenty-one centimeter wavelength, hydrogen hyperfine proton/electron spin-flip transition (from parallel to antiparallel configuration, id est: from the higher energy state to the lower energy state), electromagnetic radiation