A pure sequence groups consecutive ranks of the same suit without using a joker as a substitute. Understanding that condition helps you distinguish a completed group from a group that still needs a card.
A simple example
The 4, 5 and 6 of hearts are consecutive and share a suit. They form a natural sequence. The 4 and 6 of hearts with a joker standing in for the 5 do not form a pure sequence; the joker is replacing a missing rank.
Same numbers, different suits
The 4 of hearts, 5 of clubs and 6 of hearts are consecutive in rank but do not share a suit. Lining them up in numeric order does not make them a sequence.
Check the role of the joker
The key question is whether a card is substituting for a missing rank. Some formats allow a card of the designated wild rank to count naturally in its own suit. Check your game’s rules instead of treating every wild-rank card in the same way.
One sequence is not the whole hand
Completing a pure sequence does not by itself establish a valid declaration. The remaining cards and any additional sequence requirements must also be satisfied. Read the rules overview and check every group before declaring.