sure;  no mistaking it;  for certain;  without doubt
 mistake;  error;  accident;  mishap;  improper conduct (e.g. between man and woman);  indiscretion
 madness;  madman;  enthusiast;  freak;  junkie
 misunderstanding;  misapprehension;  false impression;  to be mistaken;  to have the wrong idea
 misunderstanding;  mistaken idea;  wrong guess
 wrong (guess or estimate);  misdirected;  irrelevant;  off the point
 out-of-place;  inappropriate;  sticking out like a sore thumb
 crossing without meeting (e.g. letters in the post, people on the road);  going astray;  difference of opinion;  misunderstanding;  estrangement
 an order of magnitude higher;  off by a digit;  in a different league;  unbelievable;  incomparable;  unimaginable
 an order of magnitude higher;  off by a digit;  in a different league;  unbelievable;  incomparable;  unimaginable
 great difference;  major mistake
 mistaking one person for another;  (case of) mistaken identity
 passing each other;  missing (meeting) each other;  failing to meet;  (being at) cross purposes;  discrepancy
 difference;  disagreement;  conflict;  clash;  discrepancy;  inconsistency
 diagonal cross;  x-shaped cross
 misunderstanding;  misapprehension;  false impression;  to be mistaken;  to have the wrong idea
 (brother and sister) born of a different mother
 wrong (guess or estimate);  misdirected;  irrelevant;  off the point
 barely miss (meeting someone, catching a train, etc.)
 off-topic (on an online thread)
 out-of-place;  inappropriate;  sticking out like a sore thumb
 wildly different (in ability, strength, etc.);  on another level;  in a different league;  of different heights;  uneven
 imprudence;  misbehavior;  misbehaviour;  misunderstanding
 mistaken idea;  misunderstanding;  wrong impression
 barking up the wrong tree;  calling at the wrong house
 variation in color (colour);  having a different color
 cramp;  sprain;  unreasonableness;  absurdity;  illogical;  unreasonable
 crossing without meeting (e.g. letters in the post, people on the road);  going astray;  difference of opinion;  misunderstanding;  estrangement
 mistaken memory;  trick of the memory;  slip of the memory
 difference in social standing;  difference in social position
 out of one's line;  out of one's field
 putting (up) in the wrong place;  hanging in the wrong place;  disagreement;  conflict;  crossing paths without meeting;  missing each other
 wrong idea;  delusion;  indiscretion;  false step;  misstep
 failing to recognize;  failing to recognise;  mistaking for
 misjudgment;  misjudgement
 half-sibling (by a different father);  uterine sibling;  maternal half-sibling;  half-brother;  half-sister
 kink in one's neck;  sprained neck
 error in judgment;  error in judgement
 kink in one's neck;  sprained neck
 miscalculation;  disappointment
 parent's cousin;  first-cousin once removed
 (being in the) wrong category;  being wrongly categorized