Namely / even up to (乃 / 乃至)

Structure A + 乃(是) + B (emphatic copula) ／ … + 乃至(于) + extreme case

乃 (nǎi) is a Classical Chinese word still alive in cultured language, with two uses. (1) As an emphatic COPULA, it means "is precisely / is none other than": 失败乃成功之母 = "failure is precisely the mother of success"; 乃是 reinforces that "is" with gravity. (2) 乃至 and its variant 乃至于 mean "and even, up to", marking an ESCALATION: after listing something, a larger or extreme case is added, 全国乃至全世界 = "the whole country and even the entire world". It belongs to literary and essayistic register; in speech one would say 是 or 甚至.

Examples

失shī败bài乃nǎi成chéng功gōng之zhī母mǔ。
Failure is precisely the mother of success.
诚chéng信xìn乃nǎi是shì立lì业yè之zhī本běn。
Integrity is none other than the foundation of any enterprise.
这zhè项xiàng技jì术shù影yǐng响xiǎng全quán国guó乃nǎi至zhì全quán世shì界jiè。
This technology affects the whole country and even the entire world.
此cǐ举jǔ关guān乎hū个gè人rén乃nǎi至zhì于yú整zhěng个gè行háng业yè的de未wèi来lái。
This move concerns the individual and even the future of the whole industry.

Levels are indicative: they follow the standard Chinese Grammar Wiki (AllSet Learning) progression, not an official HSK 3.0 mapping. We never assign levels by eye.

This point and the other 370, with audio on every example, inside Wanyu.