Yeah. The best analogue to English is like saying "suicide" versus "killing oneself." I think "seppuku" is the more proper term, but I've also heard "hara-kiri" is the "polite" form and "seppuku" is the harsh version. I don't speak Japanese, so I don't know.
ok then, if cost was not a factor whatsoever what would be the best metal to make a Bat'leth with? What metal is both the strongest and lightest available?
Nothing. Steel is ideal for swords. There are stronger and lighter metals, sure, but they tend to be more brittle. Brittle is not something you want for a sword.
HA! I think the best part is that over half the article has to explain what the weapon is, where it's from, what it's called, and about Klingons and "Star Trek".
This story also made the news on SNL last night. The joke was something like "A Colorado man robbed 2 convenience stores with a Bat'leth which is a Klingon sword from Star Trek. We're pretty sure he wasn't stealing condoms." I was pretty tired so I may have the wording wrong, but still pretty funny.