From
Old Latin neuter of similis (with u before l pinguis, i.e. [ɫ]).
adv
not-comparableat the same time; simultaneously
not-comparableand at the same time; and also; both … and (at once); together; not only ... but at the same time
“Obstipuit simul ipse simul perculsus Achātēs
laetitiāque metūque
Not only [Aeneas] himself was astounded, but at the same time Achates had been struck with both joy and fear.
(or, more concisely:)” — [Aeneas] and Achates both were astonished, stricken with joy and fear.
not-comparabletogether
“natā simul, moritūra simul, simul īte sub undās corpora!” — Born together, about to die together, together [your] bodies go beneath the waves!
(Twin babes Romulus and Remus are abandoned along the banks of the Tiber.)