This study investigates characteristics of stance-related discourse function, stance strength, and polarity in uses of the word `yeah.' In an annotated corpus of 20 talker dyads engaged in collaborative tasks, over 2300 `yeahs' fall into six common stance-act categories. While agreement, usually with weak, positive stance, accounts for about three-quarters of the instances, opinion-offering, convincing, reluctance to accept an idea, backchannels, and no-stance represent other common stance-related uses. We assess combinations of acoustic-prosodic characteristics (duration, intensity, pitch) to identify those which differentiate these stance categories for `yeah' and to determine how they relate to levels of stance strength and polarity. Differences in vowel duration and intensity help to differentiate these fine-grained functions of `yeah.' Within the larger agreement category, we can further assess the effects of stance strength and polarity, finding that positive polarity is signaled by higher pitch, lower intensity, and longer vowel duration, while greater stance strength shows higher pitch and intensity. Finally, a small set of negative `yeahs' is examined for more specific stance functions which may be distinguishable by differing pitch and intensity contours.