Critical circumstances can justify provisional safeguard duty when imports increase and threaten domestic industry disruption. Definitions govern transitional product-specific safeguard duties: critical circumstances allow provisional safeguard duty where imports have increased in absolute terms or relative to domestic production and threaten market disruption; interested parties include exporters, importers, foreign governments, domestic producers and trade associations; like article means identical or alike articles; provisional duty denotes a provisional safeguard duty under the Act; undefined terms derive meaning from the Act.