yhdennlainen
Yhdennlainen is not a recognized term in standard Finnish dictionaries and does not have an established meaning in Finnish linguistics. In practice, the form is generally regarded as a misspelling or a nonce (invented) word rather than a conventional lexical item. When readers encounter it, the most likely intention is that the writer meant a more standard form, most plausibly yhdenlainen or yhdenainen, though these forms themselves are uncommon and their exact interpretation depends on context.
If the intended meaning is to describe something of a single kind, the more natural and widely
Usage guidance for writers and editors is to rely on context to clarify meaning and, when possible,
See also: Finnish language, Finnish orthography, word formation with the suffix -lainen, disambiguation pages.