いかに

いかに is the written word for "how": how far something is true, or the way something is done. It goes in front of the clause it asks about, and that clause usually ends in か and sits inside a larger sentence.

Inside the か clause, a verb or an い-adjective is in the plain form. A な-adjective or a noun takes である or nothing, never だ: ×いかに深刻だか.

いかに〜ても – "no matter how"

With ても, or with the volitional and と, いかに means "no matter how": the outcome holds however far the first part goes.

The way something is done

いかに also asks about manner: "how", "in what way". いかにして puts the weight on the means: "by what means". Either way the clause usually ends in か or のか.

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いかに belongs to essays, speeches and formal writing, and in conversation it sounds stiff or theatrical. In speech, degree is どんなに or どれほど, "no matter how" is どんなに〜ても, and manner is どうやって or どのように.

いかにも looks similar but is a different word, meaning "truly" or "every bit": いかにもたか高そうだ is "it looks really expensive".