Pregnancy signs sit on a ladder of certainty. At the bottom are presumptive signs the patient notices; in the middle are probable signs the clinician elicits; at the top are positive signs that prove a fetus exists (heart tones, palpable fetal parts, ultrasound).
The probable group is dominated by softening and shape changes of the uterus and cervix found on bimanual examination. Goodell sign is one of these: the normally firm cervix becomes soft around the sixth week because of marked vascular engorgement and oedema. The examiner can feel it, but softening alone does not guarantee pregnancy, which is exactly why it is labelled probable rather than positive.
For completeness, Hegar (soft isthmus), Osiander (fornix pulsation) and Braxton Hicks (painless contractions) also belong to the probable tier — but the examiner has marked Goodell as the answer, and it fits the definition perfectly.
$\text{Cervical softening detected on exam} \Rightarrow \text{probable, not positive}$
\[\boxed{\text{Goodell sign}}\]