gratuitous

adj.

免费的，无偿的；无必要的；无故的，无理由的；

1. I did not want to be singled out for gratuitous punishment.
   我不愿意被叫出来遭受这无缘无故的惩罚。
2. His films are full of gratuitous violence.
   他拍的影片充满了不必要的暴力。
3. His criticism is quite gratuitous.
   他的批评完全没有根据。

Gratuitous Promises in Economics and Law
The capture and gratuitous disposal of resources by plants.
Galactose as gratuitous inducer of GAL gene expression in yeast growing on glucose
Gender‐related reactions to gratuitous sex appeals in advertising
Galactose as a gratuitous inducer of GAL gene expression in yeasts growing on glucose.
Gratuitous overexpression of genes in Escherichia coli leads to growth inhibition and ribosome destruction.
Enigmatic Gratuitous Induction of the Covalent Flavoprotein Vanillyl-Alcohol Oxidase in Penicillium simplicissimum
An Xanthomonas citri pathogenicity gene, pthA, pleiotropically encodes gratuitous avirulence on nonhosts
Fusion of GAL4-VP16 to a steroid-binding domain provides a tool for gratuitous induction of galactose-responsive genes in yeast
Induction of metallothionein-I mRNA in cultured cells by heavy metals and iodoacetate: evidence for gratuitous inducers.