Was heißt »Expertise« auf Englisch?

Das Substantiv Expertise lässt sich wie folgt von Deutsch auf Englisch übersetzen:

Synonyme

Ahnung:: foreboding; presentiment
Begutachtung:: assessment
Beurteilung:: judgement
Bewertung:: assessment; grade; marks; scores; valuation
Einschätzung:: appraisal; assessment; estimation; evaluation
Fähigkeit:: ability; capability; skill
Gutachten:: expert opinion; expert report; report; statement
Horizont:: horizon
Kenntnis:: acquaintance; cognizance; knowing; knowledge
Know-how:: know-how
Kritik:: criticism; critique
Rüstzeug:: know-how
Stellungnahme:: opinion; standpoint; statement
Urkunde:: certificate; deed; record
Urteil:: court decision; court judgment; judgement; judicial decision; verdict
Wissen:: knowledge
Zeugnis:: testimony

This is outside my area of expertise.
They had a legacy system that they have tinkered with for years and it became more and more difficult to find the expertise to improve it.
You know how much I appreciate your expertise.